Emergency loans given to RBS and HBOS were essential for stability in the banking system, the Chancellor has said.
In an emergency statement to the Commons, Alistair Darling defended the Bank of England's bridging loans to RBS and HBOS last year.
A debate had been called for by Liberal Democrat Treasury spokesman Vince Cable.
The chancellor spoke following the revelation on Tuesday that the two banks have been kept afloat by a secret loan of £61.6bn last autumn.
Both banks repaid the loans by January 2009.
Darling told the Commons that the world had been on the "brink of collapse" 12 months ago and that protecting retail depositors and maintaining financial stability had been paramount in its decision making.
"The Governor’s decision to make emergency liquidity available was quite right, and we supported it," he said.
Darling said that in his view it is "essential" that the Bank of England has the discretion to provide emergency liquidity assistance when it judges it is necessary to do so.
He added that over the last year "extraordinary support in what were extraordinary times" had been provided.
"I have kept the House informed, in numerous statements, and made it clear that we will do whatever it took to stabilise the banking system," he told MPs.
"As a result, no savers in UK banks or building societies have lost money. Inevitably, some of the support had to be provided on a confidential basis – something most people recognise.
"The judgement as to when it is the right time to disclose such operations is a fine one, but I support the Governor’s decision to disclose this information yesterday."
Shadow chancellor George Osborne said the news had highlighted the fundamental need for reform of the banking regulation system.
He said it was important that the Bank had the necessary function to lend in a case of last resort.
Osborne added: "It raises the question of how these banks came so close to collapse in the first place."
Vince Cable said he agreed in principle with the action taken but questioned why there had been such a delay in announcing the details of the loan in public.
He also questioned whether it was true to say there had been no cost to the taxpayer from the loans.
