LONDON (AP) — British Prime Minister Rishi Sunak fired the chairman of his ruling Conservative Party Sunday over a “serious breach” of the ministerial code.

Pressure had been building on Nadhim Zahawi amid allegations he settled a multimillion-dollar unpaid tax bill while he was in charge of the country’s Treasury.

In a letter to Zahawi, Sunak wrote he had been forced to act after promising at the start of his tenure that his government “would have integrity, professionalism and accountability at every level”.

Zahawi, the founder of polling website YouGov, had acknowledged a dispute with tax authorities, but argued his error was “careless and not deliberate”.

The British media reported the settlement came to almost 5 million pounds ($6.2 million).

Zahawi headed the UK Treasury from July to September 2022 in the final months of Boris Johnson’s time as prime minister.