Paul Ryan, the speaker of the House of Representatives, has announced he will not be seeking re-election in November, in a blow to Republicans' confidence ahead of the race.

The departure of Mr Ryan, the most senior Republican in the House and their biggest fundraiser, is the most prominent in a series of Republican retirements in recent months.

The lawmaker denied that the party's uphill battle to maintain control of Capitol hill had driven his decision, saying he was relinquishing his role to spend more time with his wife and three children.

“I have been a member of Congress for almost two decades. My kids weren’t even born when I was elected,” Mr Ryan said.

“What I realise is, if I’m here for one more term, my kids will only have ever known me as a weekend dad.

"I just can’t let that happen, so I will be setting new priorities in my life.”

Some will see Mr Ryan's retirement as as a sign of the uncertainty over whether the party can maintain control of the House in November's elections.