CHaNCELLOR George Osborne's GBP10 billion tax raid on the profits of North Sea oil and gas companies risks undermining the Government's credibility on taxation, MPs have warned.  The Commons Treasury Committee said yesterday that Mr Osborne's Budget announcement last month that he was raising the levy on the firms to fund a cut in fuel duty had come less than a year after he promised the industry a stable tax regime.  It said the measures set out in the Budget on energy prices - from scrapping the fuel duty escalator to the introduction of a carbon "price floor" to encourage cleaner energy sources - "lack overall coherence" as a package. The decision to increase the supplementary oil and gas levy by 12 per cent drew a furious response from the industry, which complained there had been no consultation. Some firms warned they would now be reviewing their North Sea investments.  The committee said that the way the issue had been handled "may weaken the Government's credibility in seeking to establish a stable tax regime in this and other areas".  It added: "Such reversals of policy in the absence of changes of circumstances that would warrant