The New York congressman Peter King will not seek re-election in 2020.

At least 20 House Republicans have now announced they will not seek re-election, as the party faces strong electoral headwinds under Donald Trump. Three other GOP lawmakers have resigned.

King, 75 and elected for 14 terms since 1993, said in a Facebook post he wanted “flexibility to spend more time” with his children and grandchildren.

“The prime reason for my decision was that after 28 years of spending four days a week in Washington DC, it is time to end the weekly commute and be home in Seaford,” he wrote.

It was generally noted that his win in the 2018 midterms was his narrowest of all, with 53% of the vote.

King represents parts of Long Island and is the longest-serving Republican member of New York’s congressional delegation.

He has cultivated a reputation for bipartisanship while maintaining a hard line on immigration and crime, winning issues in a district which covers suburban Long Island about an hour’s drive east of Manhattan.

He is also a former chair of the House homeland security committee and a leading voice on terrorism and its threat to the US.

King is a proud Irish American. But in the words of the New York Times in 2011, when the congressman was holding hearings on the radicalisation of American Muslims: “Long before [King] became an outspoken voice in Congress about the threat from terrorism, he was a fervent supporter of a terrorist group, the Irish Republican Army.”

In the 1980s, King was closely linked to the nationalist fundraising group Noraid and famously proclaimed: “If civilians are killed in an attack on a military installation it is certainly regrettable, but I will not morally blame the IRA for it.”

In 2011, King likened the IRA to the African National Congress and the Irgun.

“I understand why people who are misinformed might see a parallel,” he said. “The fact is, the IRA never attacked the United States. And my loyalty is to the United States.”

The troubles in Northern Ireland, he said, were “a dirty war on both sides”. But in the 1990s, he played a key role in talks which led to peace in Northern Ireland under the Good Friday agreement, acting as a go-between for Bill Clinton and the Sinn Féin leader Gerry Adams.

In 2009, it was reported that Barack Obama offered King the chance to be US ambassador to Ireland but the congressman declined.