George Osborne faces mounting pressure from Tory backbenchers to cut the top rate of tax from 45p to 40p after official figures showed that the rich paid £9 billion more in tax since the 50p rate was cut.
Tory MP John Redwood said that the HM Revenue and Customs stats, which showed that the total income tax take from earnings taxed over £150,000 increased from £40 billion last year to £49 billion this year, showed that the Treasury should go even further in setting a "competitive rate".
David Ruffley, a Conservative member of the Treasury select committee, warned that rates above 40p were "self-defeating".
He told the Times: “We should absolutely go back to 40p. It is not an accident that from 1997 until 2009, successive Labour chancellors and prime ministers did not seek to increase the 40p rate.
"There was no debate about it. It was seen as the optimal tax rate. Most Tories want to get back to what was the economic and political consensus that was 40p. We’re not saving millionaires, we just want to get back to the best way to raise money.”
However, Labour Treasury spokeswoman Shabana Mahmood said that it was “very misleading” to argue that cutting the 50p tax rate had resulted in the rich paying more as they had simply delayed their income in the knowledge until the top rate was cut.
“Many of the highest earners moved income and delayed bonuses by a year after George Osborne’s 2012 Budget in order to benefit from the top rate tax cut," she said.
"For example, bonuses in financial services jumped by 83% in April 2013 as bankers waited until the after the top rate tax cut before paying themselves bonuses. Far from boosting tax revenues this shifting of income will actually have cost the Treasury millions of pounds in lost revenue."
The increasing calls for the chancellor to back a 40p top rate of tax comes soon after Graham Brady, head of the 1922 committee which represents Tory backbenchers, urged the leadership to drop its defensive "rigmarole" in justifying why the 50p rate.
"I think the government makes unnecessarily heavy weather of it sometimes," he said, during a question and answer session after delivering this year's Keith Joseph Lecture in Westminster.
Ministers "end up getting into a big rigmarole of how the wealthy are paying more in tax than under previous Labour governments" when questioned about the decision, he added.
"The simple answer surely for Conservatives is of course we believe in lower taxes and we believe in lower taxes for everyone, and we believe it is more efficient and increases their incentives to work hard," he concluded.
The senior backbencher said that Osborne should have gone further and cut the top rate of income tax all the way to 40p rather than a "halfway house" of 45p.
"The politics of that was very straightforward and it really wouldn't have made any difference to the popularity or the unpopularity of the measure if you went from 50p to 40p rather than 45p. In some ways we've just made it more difficult for ourselves [and] we've left an unnecessary complication in the tax system as well."