Chancellor Rishi Sunak has denied "ignoring" fraudulently claimed Covid support funds worth billions of pounds.
Mr Sunak said the UK government would "do everything we can" to recover loans stolen by fraudsters.
On Monday, a Conservative minister resigned over the government's "woeful" efforts to stop abuse of pandemic support schemes.
The government last week disputed reports it had written off £4.3bn of loans.
Announcing his resignation in the House of Lords, Treasury minister Lord Agnew accused the Treasury of having "little interest in the consequences of fraud to our society" and of making "schoolboy errors" over the awarding of loans.