Labour turned independent MP John Woodcock has said he will not stand at next month's general election.
The Barrow and Furness MP quit Labour in July last year and had planned to stand at the 12 December poll as an independent.
The 41-year-old made the announcement as he revealed he and his partner are expecting their first child.
He told constituents "life plans had changed" following news his journalist partner Isabel Hardman was pregnant.
He said they had been blessed with "unexpected, but wonderful" news.
Mr Woodcock has represented the Cumbrian seat since 2010, winning it with a 209 majority in 2017.
A long-time critic of Labour leader Jeremy Corbyn, he claimed the party had been "taken over by the hard left" and "tolerated" anti-Semitism.
In his letter he said: "I am suddenly changing my life plans because my partner and I have been blessed with an unexpected but wonderful piece of news - Isabel is expecting a baby.
"We are both delighted, but the impending arrival means my life has to change."
He said he did not feel able to continue as an MP, spend time with two children from a previous marriage in Scotland and devote time to his new family.
"Something has to give", he added.
He said he hoped to remain in Barrow and "contribute to public life".
He praised the community of west Cumbria as people who "always look out for each other".
London-born Ms Hardman, 33, is assistant editor of The Spectator.
Mr Woodcock, who is on the right of the party, had the Labour whip withdrawn in April 2018 amid claims he sent inappropriate messages to a former female member of staff.
He has said he does not accept the charges and was fully co-operating with an internal inquiry.
Announcing his resignation from the party, he accused Labour of failing to appoint an independent investigator to rule on the disciplinary case.