Miller, the acting IRS commissioner, resigned due to anger as to why the agency used terms such as “tea party”, for example, to subject some groups’ applications for tax-exempt status to tougher scrutiny. The behaviour has prompted some on the conservative and libertarian side of the political spectrum to accuse the IRS of being used as a political weapon by the administration of Barack Obama against his ideological foes.

The scandal comes at a sensitive time for the Obama administration, already under fire for its handling – or mishandling - of the attacks of the Benghazi embassy in Libya last September, and also for allegations over the tracking of telephone records of Associated Press journalists.

Speaking about the IRS issue, Obama announced Miller’s departure in televised comments at the White House. He said: “It’s inexcusable, and Americans are right to be angry about it, and I am angry about it. It’s important to institute new leadership that can help restore confidence.”

Suggestions that the IRS had used its scrutiny to go after political groups is particularly sensitive at a time when this organisation’s powers are continuing to expand, such as through enforcement of complex, and controversial, rules such as FATCA, or the Foreign Account Tax Compliance Act.