ENERGY Secretary Chris Huhne has been challenged to  come clean  over the UK Government s decision to pull out of the groundbreaking carbon capture and storage project at Longannet in Fife.  Bill Walker, the SNP MSP for Dunfermline, said it was time for straight answers after ScottishPower s chief corporate officer Keith anderson said cost was the reason for its cancellation.  Mr Walker said Mr Huhne had been caught out over claims there were technical problems and both he and Scottish Secretary Michael Moore owed Fife residents an explanation.  Mr Walker hit out after Mr anderson said the engineering and design study for the project had been a huge success but the companies involved in the consortium had reached a point where the question was asked if the Government believed in the current climate if this was a sensible use of ?1.5 billion, half a billion more than the Government wanted to spend on the trial.  Mr anderson said:  They came back and told us    No, therefore we have to bring the process to an end .  Mr Walker said:  UK ministers were happy enough to visit Longannet for publicity and pictures but were not willing to put up the long-term investment that would put Scotland and Fife at the front of clean-energy generation and boost employment across the area.  Chris Huhne has been caught out. ScottishPower is clear it could be done and that there are no technical difficulties. The LibDems and UK Government owe the people of Fife a straight answer.  The more information that emerges about the UK s actions over Longannet the bigger the questions over what the Scottish Secretary has actually been doing for Scotland.