An influential report recently labelled the IFRS rules a "fiasco" that caused banks to produce "false profits and overstated capital". But Tweedie labelled his critics' arguments "baloney", saying banks would not have been able to understand the full gravity of their losses without the system.
Last month, Tim Bush, a member of the Urgent Issues Task Force - a committee set up by the Accounting Standards Board - told the House of Lords that IFRS should be scrapped in favour of the previous regime, known as UK GAAP. Bush, one of the leading critics of IFRS, had previously said the contentious rules had "misled creditors, misled shareholders, the Bank of England, the Financial Services Authority and others".
Tweedie said Bush's proposal to reintroduce UK GAAP, which was dropped by large listed companies as a method of evaluating accounts in 2005, was misguided.
"Tim Bush doesn't know what he's talking about," he said. "I was chairman of the UK Standards Board (which oversees accounting standards in Britain] when there was no standard on derivatives. The UK would have been hit with losses it never even knew it had (without IFRS]."
Criticism has also been aimed at they way assets were valued under IFRS, known as "mark to market" or "fair value" which caused banks to take billions of pounds worth of writedowns on assets.
Tweedie admitted that the "fair value" system made banks overstate losses, but he blamed financial institutions for taking account of all of these losses too late.
"It is likely fair value overstated the losses. It probably did because the market just collapsed. But the banks were very late writing down their losses. The fact is, when you have got exotic assets nobody wants, the value diminishes very fast," he said.
Tweedie called for the Basel Committee on Banking Supervision to require banks to hold back 20 per cent of their profits in order to prevent future crises. Tweedie, who has spent ten years at the head of the IASB, will step down in June 2011 to take up the chairman's role of Scottish accounting body ICAS in 2012.
In response to the crisis, Tweedie said the IASB had "tightened" rules making banks make greater disclosures on their assets. Next month, the body will also present proposals - known as IFRS9, which could replace the unwieldy and some say overcomplicated financial instruments accounting standard, IAS39 - that Tweedie says will "completely transform the accounts of financial institutions."