The head of HM Revenue and Customs (HMRC) is set to be hauled before a parliamentary committee to explain his organisation's handling of the current spate of unexpected tax demands going out to 1.4 million people.
Dave Hartnett, permanent secretary at HMRC, was forced to apologise at the weekend for the demands, which ask taxpayers to pay an additional average of £1,428 because of inaccuracies in the PAYE system.
He issued a statement saying he was "deeply sorry" after a wave of anger greeted his comment in a radio interview that "I'm not sure I see a need to apologise".
Yesterday, the chairman of the influential House of Commons Treasury Committee, Andrew Tyrie, made clear that he wants to subject Mr Hartnett to a grilling by the cross-party committee.
And he suggested that the controversy over the handling of the demands may eventually force HMRC to make further concessions to taxpayers.
Mr Tyrie welcomed the Treasury's decision to write off debts smaller than £300 - an increase from the previous threshold of £50.
And he told BBC Radio 4's The World At One: "What may, I think, turn out to be a cock-up in the handling may result, in the long run, in greater concessions of that type than the Government would otherwise have needed."
The Treasury Committee has yet to decide whether to call Mr Hartnett to give evidence on the PAYE errors, which will also result in millions of taxpayers receiving rebates.
But Mr Tyrie left little doubt that he wants the chief taxman to face questions.