Technicians from a Chinese company considered the frontrunner in the race to buy the $9 billion NSW electricity network were thrown out of the Philippines earlier this year over national security concerns.
The revelation comes in the wake of controversy over the granting of a 99-year lease on the Port of Darwin to a Chinese company with links to the People's Liberation Army, and indications that the lease was not subject to proper foreign investment scrutiny.
Opposition Leader Bill Shorten has asked Prime Minister Malcolm Turnbull for an urgent briefing on the process that allowed the port lease to be approved, saying he was "seeking reassurances regarding the due diligence analysis that has been done on the national security risks" of the port deal.
"Additionally, from public reporting of the deal it is unclear whether a full Foreign Investment Review Board process was undertaken to assess the impact of the lease arrangement," he said. 
"I ask for your clarification about what FIRB process was undertaken in this instance".
The Australian Financial Review reported last week that the bid for the port by the Landbridge Group appeared to have slipped through the net of the Foreign Investment Review Board.
This was confirmed by Treasurer Scott Morrison on Friday who told the Financial Review the "rules Labor had in place and that the shadow treasurer presided over did not permit [the port] transaction to come under FIRB's review".
Mr Morrison made the comments as he signalled the government was looking to strengthen protections of strategic national assets and critical infrastructure, amid controversy over the Port of Darwin lease deal and ahead of final bids being made for the $9 billion NSW electricity network this week.
"The government is acutely aware of the sensitivities regarding foreign investment in strategic national assets and critical infrastructure," Mr Morrison said on Friday.
"The government is assessing options to strengthen the federal government's ability to protect the national interest in these cases and we will have more to say on this issue in the future."
However, sources do not believe it is possible for the federal government to overturn the deal between the Northern Territory and Landbridge.
The furore over the transaction has provoked behind the scenes recriminations between Darwin and Canberra and within the federal government.

Focus shifts to NSW power sale
But it has also put the spotlight on the process for considering bids for the NSW power grid - which includes fibre optic cables used by Australian defence and intelligence facilities. Final bids on the grid are due this week.
The NSW government has opted not to put foreign ownership limits on the bid, instead opting to leave any national security issues to Canberra. 
Earlier this year, the Philippine's government refused to renew the work visas of 16 Chinese experts employed by the National Grid Corporation of the Philippines when they expired in   July.
The Diplomat website reported that the Chinese state-owned firm State Grid Corporation of China has had a 40 per cent stake in the NGCP which runs the national power grid of the Philippines.
State Grid is now part of a consortium, which includes Macquarie Bank, bidding to buy the NSW power grid, known as TransGrid.
Philippines energy secretary Carlos Jericho Petilla??? said the government now wanted only Filipinos working there.
Mr Petilla openly acknowledged that concerns over the presence of the Chinese experts stemmed partly from the ongoing South China Sea disputes between the Philippines and China.
But he also admitted that some officials in Philippines government agencies and bodies like the National Security Council were uncomfortable with the national electricity grid having Chinese experts involved.
"NSA is wary that it [NGCP] is being run by Chinese nationals. So ang solusyon [the solution] is with finality, turn over everything to Filipinos," he said in a mixture of Tagalog and English.
The Diplomat website went on to report that "interestingly, Petilla also reportedly wondered aloud why others did not have similar fears because the Chinese firm also has similar partial ownership in other countries like Australia".
"If we are paranoid about it, I am not sure why Australia and others are not", he said.
State Grid was given FIRB approval in 2013 to buy 19.9 per cent of AusNet from Singapore Power in 2013 on the condition, according to then Treasurer Joe Hockey, that "at least 50 per cent of the members to be appointed by State Grid ??? are Australian citizens who are ordinarily resident in Australia".
It was reported in   July that Singapore Power had been forced to deny being in collusion with State Grid to block a decision of AusNet to bid for TransGrid. The two companies also ended the term of non-executive director Tony Iannello,who was leading the bid for the NSW grid.
State Grid is now bidding separately for TransGrid with Macquarie Bank.
The corporation already owns part of Melbourne's electricity network, the NSW gas distribution grid and the main gas pipeline from Bass Strait to Sydney.
Intelligence agencies have made clear their alarm about the national security implications of State Grid's bid. But it is an issue that has largely been seen in the context of NSW politics, rather than national politics.
This is despite the fact that NSW Premier Mike Baird has made it clear he is batting such assessments through to Canberra.
The  Financial Review reported last week that tough national security requirements were expected on foreign bidders for the $9 billion network.
Chinese companies bidding for the network would be prevented from having any staff in management positions and directors would require a security clearance, under the terms of FIRB approval.

Darwin port buyer has PLA links
The Australian Strategic Policy Institute revealed last week that the company that has won the Port of Darwin lease, Landbridge, had strong links with the People's Liberation Army.
China specialist Geoff Wade wrote on ASPI's Strategist blog that "as if to underline the party-state links of the company, in   August last year, with the support of the People's Liberation Army, Landbridge established a people's armed militia within the company" under the leadership of He Zhaoqing". He, an ex-PLA officer, is the secretary of the branch committee of the Communist Party which oversees Landbridge's operations.
"In short, Landbridge is a commercial front intimately tied to state-owned operations, the party and the PLA", Wade wrote.
Wade posted an English translation of a page from the Landbridge's Chinese-language website.
"The Landbridge Group, as a large-scale civilian enterprise has, through 20 years of unstinting effort, established its four major commercial planks of petrochemicals, port logistics, real estate and tourism and international trade", the website says. "Throughout, the Landbridge group has firmly upheld the ideal of "a strong enterprise does not forget to repay the country, while a prosperous enterprise does not forget national defence".
"It has actively supported the army through culture and supported the army through science and technology. It has resolved difficulties and served as a logistic backup for military units engaged in maritime training, and for the military units based in Rizhao. The Landbridge Group has been assigned the appellation of a double model for 'Loving Lanshan and Putting Efforts into Strengthening the Military'."
Landbridge released a statement on Friday saying the claims were "inaccurate and wrong".
"Landbridge Group is not a state-owned enterprise. It is a private company owned by the Ye Family," the statement said. "Landbridge made a full application to the Foreign Investment Review Board in connection with the acquisition of the port and consulted extensively with FIRB and the Department of Defence in the lead-up to the bid."
It claimed pictures of "security staff" had been misconstrued as armed militia but were actually part of the fire fighting service.
Northern Territory Chief Minister Adam Giles said that while the deal had not been through formal FIRB processes, it had been given the go-ahead by both FIRB and the Department of Defence. 
He dismissed criticism of the deal as "xenophobic" and rejected Labor's call for a new review. 
"It's through the proper process and they are happy with it. I'm 100 per cent happy with it. It's done and dusted. The money is in the bank," Mr Giles told AFR Weekend.
 "We went to FIRB and they said, 'We've already approved this company, we're fine'. So FIRB approved it and Defence said fine. There's been proper process."

 Chinese news reported that Landbridge Chairman Ye Cheng's business card even says he is a member of the CPPCC National Committee, the Chinese government's official political advisory body.
Netease journalist Meng Lingjuan reported last week that his business card reads: "Landbridge Group Ye Cheng, a member of the CPPCC National Committee, the Shandong Provincial People's Congress, Landbridge Group Chairman, president".