British Prime Minister Rishi Sunak has dismissed the chair of the ruling Conservative Party, Nadhim Zahawi, over his tax affairs.

Zahawi, a co-founder of major pollster YouGov, was first elected as a member of Parliament in 2010.

Multiple British media outlets said tax authorities had pointed out irregularities in tax payments related to his firm's business.

In September last year, Zahawi agreed to pay back tax and a penalty totaling about 5 million pounds, or about 6.2 million dollars. He was then finance minister under former Prime Minister Boris Johnson.

But Zahawi reportedly failed to disclose the fact when he was appointed party chair.

Sunak said on Sunday, "It is clear that there has been a serious breach of the Ministerial Code."

The scandal is likely to deal a blow to the Sunak administration, which has been struggling with low approval ratings.

The latest opinion polls show the government's approval rating is 14 percent. Sunak will mark his 100th day in office on Wednesday.

There are growing calls for Sunak to take responsibility for Zahawi's appointment.