Gordon Brown has called for an end to the “age of irresponsibility” in the financial sector, his most frank acknowledgement so far that the City was allowed to run wild while he was Chancellor.

Speaking to the UN in New York, the Prime Minister said that global financial institutions had been acting with impunity and needed greater supervision. As negotiations continued in Washington to secure agreement on the $700 billion Wall Street bailout, Mr Brown repeated his backing for the deal, suggesting that agreement had been reached by all parties in principle.He flew to Washington after President Bush agreed to interrupt negotiations for a 90-minute meeting at the White House.

After the meeting Mr Brown said that he supported the bailout “whatever the detail” while Mr Bush said the plan would be approved by Congress.

Earlier Mr Brown had warned the UN General Assembly that the world urgently needed to regain confidence in the financial markets and banks. “Confidence in the future is needed to build confidence today and that confidence will be built by showing that what are global problems can also be addressed by globally co-ordinated solutions,” he said.

“This has been an era of global prosperity. It has also been an era of global turbulence and where there has been irresponsibility we must now say clearly that the age of irresponsibility is over.” Downing Street refused to say how long Mr Brown believed that the age of irresponsibility had lasted.

Asked for an example of irresponsibility, Mr Brown’s spokesman cited the way financial institutions had built up huge liabilities that they were now unable to deal with or quantify.

Critics seized on his remarks as an acknowledgement that he must shoulder some of the blame for the current crisis. George Osborne, the Shadow Chancellor, said: “ For ten years he presided over a debt-fuelled boom and failed to call time on debt. The age of irresponsibility has now become the age of hypocrisy.”

Mr Brown is using the US visit, his third as Prime Minister, to build a package of reforms to force companies to declare the full extent of their liabilities. “We must now build a new global financial order founded on transparency not opacity, rewarding success not excess, responsibility not impunity and which is global not national.” He also wants an early warning system to alert all global regulators of problems; greater obligations on company directors to prevent them from behaving irresponsibly; and more pressure to be applied to align salaries and bonuses with long-term gain and stability. “No member of senior management should be able to say they did not understand the risks they were running and walk away from their obligations.”

Mr Brown travelled to New York straight from the Labour Party conference in Manchester on Wednesday and had been due to fly home this afternoon.

The original purpose of the trip had been to secure more financial commitments to help developing countries, with another $16 billion committed by governments and business to achieving the Millennium Development Goals.

After the events of the past fortnight, however, the focus inevitably switched to the global financial turmoil, with Mr Brown landing hours before President Bush gave warning that the whole of the US economy was in jeopardy.

Mr Brown met world leaders on Wednesday night and senior Wall Street fund managers on Thursday morning, followed by the head of the New York Federal Reserve. Downing Street secured last-minute agreement to see President Bush.

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