Congressman Jason Chaffetz, a Republican who has refused to investigate Donald Trump’s possible conflicts of interests, has said he will not seek re-election.

Mr Chaffetz, the House Oversight Committee chairman who played a key role in investigating Hillary Clinton during the presidential campaign, announced that he will not contest in the 2018 congressional elections.

The 50-year-old powerful figure on Capitol Hill, said he was returning to the private sector after more than 13 years as an elected official.

“I have long advocated public service should be for a limited time and not a lifetime or full career,” he said in a statement. “After more than 1,500 nights away from my home, it is time.”

The Associated Press said that Mr Chaffetz had been rumoured as a possible candidate for Senate or governor. He had enjoyed easy re-election wins in his Republican-friendly Utah congressional district.

However, he was facing a surprising challenge from a Democratic newcomer who raised more than a half-million dollars by tapping into anger over Mr Chaffetz’s recent comment suggesting people should spend their money on health insurance instead of iPhones.