There has been concern expressed following a hard-left “takeover” of the Labour Party’s influential Disputes Committee, after its longstanding chair was ousted by a Momentum-backed challenger on Tuesday.

The position matters because the Committee decided whether to formally investigate allegations of racism and anti-Semitism, or to dismiss them.

It comes after left-of-centre candidate Christine Shawcroft, who was supported by the influential grassroots group Momentum, beat Ann Black by 22 votes to 15, just one day after three Momentum-backed candidates won seats on Labour’s National Executive Committee, consolidating leader Jeremy Corbyn’s position.

The Committee Shawcroft now chairs has the power to progress anti-Semitism cases to Labour’s highest internal body, the National Constitutional Committee, members of which have the power of expulsion.

Lobbyists were rattled with the surprise move, with Jennifer Gerber, director of Labour Friends of Israel, saying: “The hard-left has spent two years denying Labour has a problem with anti-Semitism. They must not now be allowed to stifle investigations into it or action to combat it.”

Black, who was elected on the Grassroots Alliance slate, is the only NEC candidate ever to have received more than 100,000 members’ votes, and the vote to replace her has been “a wake-up call for the soft left,” according to Richard Angell, the director of Progress, which takes more centrist positions within Labour.

However Jeremy Newmark, chair of the Jewish Labour Movement, said he had met Corbyn’s advisers “to share concerns” and had been assured that Shawcroft had no intention of stunting the progression of cases of anti-Semitism.

It is our understanding that all of the recommendations placed before the committee yesterday on anti-Semitism cases were either adopted or strengthened,” he said. “We also understand that the Committee addressed our complaints that serious disputes are currently taking far too long to conclude.”

Newmark added: “We will judge the NEC Disputes Committee by real results and actual outputs, not by leaks and speculation.”

The next few weeks will see the NCC consider a number of high-profile cases of alleged anti-Semitism, including former Momentum vice-chair Jackie Walker. 

“The results will send an important signal to the Jewish community,” said Newmark. “Having strengthened its rules at Party Conference last year there can be no further excuses for failure to deliver a gold standard in acting on antisemitism.”