Rosie Cooper MP: why West Lancashire constituency MP has resigned - will Liz Truss face a by-election?

Rosie Cooper has announced on Twitter that she is standing down as an MP, triggering a by-election in a strong Labour Party seat.

The MP for West Lancashire, who has held a seat in Parliament for 17 years, admitted that the announcement would come as a “surprise to many people” - since she recently secured reselection to stand for the next election.

Labour confirmed that a by-election will take place in the autumn, which will be the first faced by new Prime Minister Liz Truss.

Ms Cooper wrote in her resignation announcement: "It has been an incredible honour and privilege to have served the people of West Lancashire for the last 17 years.

“I have loved every minute, even in the most difficult times.”

The 72-year-old, who has accepted a new role as chair of Mersey Care NHS Foundation Trust, added that the events she has faced over the past few years “are well documented and undoubtedly have taken their toll.”

Ms Cooper is most likely referring to her being the victim of a plot to kill her by Jack Renshaw, an alleged member of banned neo-Nazi group National Action.

This is the same group that Thomas Mair, the man who killed Labour MP Jo Cox, was a member of.

Renshaw admitted to planning to kill Ms Cooper with a 48cm replica Roman Gladius sword in the summer of 2017.

Afterwards, he was going to take hostages to lure police officer DC Victoria Henderson to the scene so that he could kill her too, the court heard.

The alleged neo-Nazi pleaded guilty to acts of terrorism and of making threats to kill a police officer, but denied a third charge of membership of National Action.

Earlier this year, Ali Harbi Ali, 26, was given a whole-life order at the Old Bailey for murdering Conservative MP Sir David Amess.

Ms Cooper previously worked as chair of Liverpool Women’s Hospital, and as a trustee of the Roy Castle Lung Cancer Foundation.

She said that returning to the NHS “felt like the right opportunity at the right time.”

The MP assured constituents however that it does not mean she cannot continue “with [her] other passion of representing the people of West Lancashire.”