Labour MP Chris Williamson has been suspended from the parliamentary party once more ahead of an urgent review of his anti-Semitism case.
General secretary Jennie Formby took the move following a backlash from party MPs, members and Jewish groups.
Chris Williamson was suspended in February after saying Labour had “given too much ground” over the issue.
However, he was allowed back in on Wednesday after an investigation by the party’s National Executive Committee.
Now, a Labour source says issues raised by an MP on the investigation panel needed to be examined.
“Subsequently, the whip is not restored as the decision is still pending,” the source said.
“There had been rumours that Watson corralled support against Williamson in fear of a much talked about Labour deputy leadership challenge.”
Labour’s general secretary Jennie Formby has written to the NEC to inform it of the issues with the investigation raised by the panel member – Labour MP Keith Vaz – and his concerns will be on the agenda for its next disputes committee meeting, said the source.
They added: “Under the party’s rule book, the general secretary and the leader of the party cannot overturn decisions made by NEC panels, which are advised by independent barristers.
“Only the NEC has the power to do so.”
There was a large backlash from Labour peers and MPs after Mr Williamson was allowed back into the party on Wednesday.
Deputy leader Tom Watson instigated more than 100 of them to sign a letter calling for Labour Party leader Jeremy Corbyn to act and remove the whip from the Derby North MP.
Seventy-one Labour politicians also wrote to the chair of the Parliamentary Labour Party (PLP), John Cryer, earlier, asking him to begin a process that could have lead to the whip being withdrawn from Mr Williamson if Mr Corbyn didn’t act.
Left wing party members have been outraged at the attacks on Chris Williamson MP by the centrist from Watson’s Future Britain group.
Mr Williamson said he “deeply” regretted the remarks and did not want anyone to think he was “minimising the cancer of anti-Semitism”.