DUP North Antrim MP Ian Paisley has confirmed he will not be standing in the general election.
Mr Paisley, 83, has been an MP since 1970. It is thought that his son Ian Paisley Jr will face TUV leader Jim Allister in the constituency.
At the last general election in 2005, Mr Paisley polled 25,156 votes, giving him a majority of nearly 18,000.
Mr Paisley was widely expected to retire as an MP after stepping down as DUP leader in 2008.
However, after the anti-powersharing TUV took almost 70,000 votes from the DUP at last year's European election, Mr Paisley signalled he was considering standing for re-election in North Antrim.
In recent interviews, he had refused to be drawn on whether he would stand again, but confirmed his decision to step down to the Ballymena Guardian on Tuesday.
Mr Paisley told the paper he had "no regrets" about deciding to share power with Sinn Fein in 2007.
"After a period of tough negotiations it was my view that, provided our conditions were met, the overwhelming majority of the people of Northern Ireland wanted me to do the deal, it was as simple as that," he said.
Mr Paisley said he was saddened that some DUP members had quit in protest, adding: "I believe I showed the leadership required to get the best possible deal in the circumstances."
Politicians and voters give their reaction to the news Mr Paisley is standing down
He first came to international prominence in the late 1960s as a hardliner and political firebrand but mellowed in recent years.
After the DUP and Sinn Fein agreed to share power in 2007, Mr Paisley formed an unlikely friendship with his former enemy Martin McGuinness of Sinn Fein. The two men were so close they were dubbed the "Chuckle Brothers".
On Tuesday, following the announcement, Mr McGuinness said he considered Mr Paisley a personal friend and still contacted him regularly.
He added: "We had the ability to sit down and talk to one another about the way forward and we were agreed on how we should move forward."
Mr Paisley, who turns 84 next month, was first elected as a MP in 1970. He has in recent years stepped down from senior positions in politics and in his Free Presbyterian Church.
His son, Ian Paisley Jr, said he did not want to pre-empt the DUP's selection meeting on Monday by saying he expected to be nominated.
"This is the end of a significant era in British politics and Ian Paisley has left giant footsteps to fill," he said.
Mr Paisley said his hardline former party colleague Jim Allister, the TUV leader who quit the DUP in protest at its decision to share power with Sinn Fein, was not a good alternative for voters.
"They certainly have a rant, they certainly have a person consumed by their own anger, hypocrisy and conceitedness and a person without a plan," he said.
"He offers nothing - his strategy is destroy the assembly and go back to direct rule - we had a generation of direct rule and that failed."
Mr Allister said his former party leader had done a "very good job" in his early years as an MP but in recent times his record was "far from impressive".
"He'd only been at 18% of votes in this parliament and missed key votes like on the referendum on Europe, abortion issues and blasphemy laws and a whole string of issues," he said.
"Obviously he wasn't able to do the job so he's given up.
"His legacy is of terrorist-inclusive government and I believe North Antrim hasn't changed, its people haven't changed and they will once more embrace the tried and tested principles of traditional unionism which they have held on to for so long."
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