|Lloyd Blankfein, the chief executive of leading investment bank Goldman Sachs, has backed George Osborne's austerity drive, telling him to "stay the course".
The Chancellor has been resisting increasing pressure to ease the £130bn programme of spending cuts and tax rises.
The IMF, European Commission President José Manuel Barroso and Pimco boss Bill Gross, who head up the world's largest bond fund, have all urged him to slow his austerity programme in the past seven days.
Mr Blankfein told Radio 4's Today programme that Britain had invested a lot in austerity and should "stay the course a little longer".
He said "it was very tough" for the Chancellor, and he could see why at this point in the cycle there were calls to "relax the throttle" and extend austerity for longer.
Christine Lagarde, managing director of the International Monetary Fund, warned in Washington last week that Britain's economic growth performance is "not particularly good", reinforcing suspicions that the IMF will urge Britain to moderate the severity and speed of his austerity plans.
The funds chief economist, Olivier Blanchard, said Mr Osborne was “playing with fire” by pressing ahead with his plans in the face of a stalling recovery.
However, Fitch, the ratings agency, argued that the UK had no “fiscal space to absorb further adverse economic and financial shocks” in its decision to cut Britain from AAA to AA+ on Friday.
Speaking in Washington, Mr Osborne hinted he would reject a likely demand from the IMF next month to fundamentally alter his austerity programme.
Asked if he would follow a different IMF plan, he said: “It depends whether you agree with that advice.”
Defending his current strategy and risking a fight with the Fund, he said: “What the IMF has asked us to do is to show flexibility and credibility. The Autumn Statement and Budget demonstrated that by not chasing the debt target and taking additional measure to support the economy.”
He was also dismissive of Mr Blanchard’s claim, saying he was “just one voice” at the IMF. He added that the IMF has recommended countries reduce their deficit at a rate of 1pc a year and “we are bang on that”.
In a speech yesterday, Mr Barroso said the policy of austerity pursued by the EU in recent years no longer has the public backing needed to work. "While I think this policy is fundamentally right, I think it has reached its limits," Mr Barroso said.
While Mr Gross said the drive to cut debt rapidly through severe austerity in Britain and the eurozone was stifling recovery. To get real growth "you've got to spend money", he told the Financial Times.