Energy consumer organisation the International Energy agency (IEa) has invited Russia and the Opec oil producers to join it, in a desperate bid to broker a peace between buyers and sellers over soaring crude prices.  The olive branch was extended yesterday by the IEa's executive director, Nobuo Tanaka, to Russia's deputy prime minister, Igor Sechin, but has already run into powerful opposition from the country's state-owned gas group, Gazprom.  In an exclusive interview with the Observer, Tanaka said it was time that producers and consumers realised they were on the same side. "We all really have a common interest. You cannot take oil in isolation from gas security, energy efficiency and electricity from renewables.  "The issues of energy security and climate change need to be tackled collectively and we think Russia and other key producers can learn a lot from [the IEa's] experience."  Producers and consumers have been at war with each other over who is responsible for high oil and gas prices. The IEa has repeatedly called on Opec to increase production, while producers blame western banks and other speculators for the volatility. Russia has recently called for the establishment of a gas cartel to match the oil cartel of Opec, something the IEa wants to avoid.  The initiative from Tanaka comes as the spike in oil and gas prices continues to make life miserable for already struggling UK households, whose living standards are being eroded by inflation. On Friday the aa said it had written to the European Union's competition commissioner asking him to investigate price volatility at the pumps, as drivers were being "ripped off". In the last month the oil price has fallen back from $126 a barrel to $110, but the aa says this change has not been reflected in retail prices.  Russia, along with China and India, already has observer status at the IEa but Tanaka said it would be a good thing if they became full members. Countries such as Indonesia and Mexico already want to become members, so "why not Russia?" he said.  Tanaka has also held preliminary talks with Saudi arabia and other Middle East oil producers about playing a role inside the Paris-based IEa. The agency was set up in the wake of the 1970s oil price shocks and has been largely regarded since then as a US-led group representing consumer nations against the power of the Opec cartel.  all the countries ins