US election 2012: George W Bush enters debate as he criticises Barack Obama's 'Buffett Tax' The plan is named after the billionaire investor Warren Buffett, who complained that he paid a lower rate than his secretary. It is unlikely to be passed by the divided US Congress, but by championing it Mr Obama hopes to highlight the low tax rate paid by Mr Romney. The former Massachusetts governor, who is worth about $250 million (£160 million) after a career in private equity, paid as little as 14 per cent thanks to Mr Bush's drastic cuts to tax on capital gains and investment returns. The former president on Tuesday defended his "Bush tax cuts" for higher earners, which opponents claim have cost the US more than $1.08 trillion (£681 billion) in lost revenues over the past decade. Extended by Mr Obama in December 2010 amid dire economic circumstances, the cuts are again due to expire at the end of 2012. Mr Obama would let them die while Mr Romney would extend them. The former president said on Tuesday that he wished they "weren't called the Bush tax cuts," suggesting they would be less likely to be raised if they did not bear the name of such a divisive figure. He announced that a think-tank set up in his name would publish a book later this year outlining a plan to return the US to healthy growth. "It's got to be a staggering thing for the cynics," said Mr Bush. They didn't think I could read, much less write a book.