Labour MP Conor McGinn has had the whip suspended after a claim made about him to the party’s independent complaints process.
The St Helens North MP has also had his Labour membership suspended while an internal investigation takes place, it is understood.
Mr McGinn does not know any of the details of the complaint made against him, but said he was confident that it was “entirely unfounded” and denied any wrongdoing.
The deputy national campaigns coordinator – a key ally of leader Sir Keir Starmer – only recently returned to Westminster after he was diagnosed with a heart condition known as atrial fibrillation.
In a statement on Wednesday evening, Mr McGinn said: “The Labour party has informed me that it is automatically required to apply a temporary procedural suspension while a complaint is investigated.”
The senior MP added: “I have not been told the details of the complaint but I am confident that it is entirely unfounded. I strongly reject any suggestion of wrongdoing and I look forward to the matter being resolved quickly.”
Before taking up his role in helping Labour win more seats at the next general election, Mr McGinn previously sat on the frontbench as a shadow Home Office and shadow Cabinet Office minister.
He becomes the fifth Labour MP to have the whip suspended and face an internal probe under the party’s new complaints procedure.
Neil Coyle had the Labour whip suspended in February following claims he made racist comments towards a journalist in a Commons bar.
Rupa Huq was suspended in September after she called then-chancellor Kwasi Kwarteng “superficially” black, with Sir Keir making clear he believed what she had said was “racist”.
Nick Brown was also suspended in September following an unspecified complaint. And Christina Rees had the whip removed in October after her constituency staff made bullying allegations.
The complaints process – which sees any MP under investigation administratively suspended – was brought in earlier this year by Sir Keir in the wake of the controversy over the handling of antisemitism in the party.
The saga also saw former leader Jeremy Corbyn stripped of the whip following his response to the Equality and Human Rights Commission (EHRC) report into “serious failings” by the party during his time in charge.
Mr Starmer said earlier this week that he did not see how Mr Corbyn could stand as a Labour candidate at the next election. “I don’t see the circumstances,” he said.