Jennie Formby, a senior Unite figure and Labour NEC member, will be speaking at Momentum’s #KeepCorbyn rally this evening.

Formby is the South East Regional secretary for Unite and a key ally of General Secretary Len McCluskey. She said on Twitter she would be “proud” to speak for Unite at the Pro-Corbyn event.

More than 3,000 people are expected at the 6pm demonstration to protest the raft of resignations and called for the Labour leader to step down from the past day.

The rally was called after the first resignations from the shadow cabinet, which the Corbynite faction have labelled as a mark of “disrespect” to the membership, who gave the leader an overwhelming mandate in last summer’s leadership election.

Since yesterday morning 24 frontbenchers have resigned, with Corbyn filling ten of the most high-profile positions this morning.

Emma Rees, a national organiser for Momentum, said the interest in the event was a sign of Corbyn’s ongoing popularity with the public.

“The huge numbers of people signed up for tonight’s rally in such a short space of time just goes to show the popularity of Jeremy Corbyn and his ideas.”

“Momentum supporters are disappointed with the orchestrated Shadow Cabinet resignations. These actions are grossly irresponsible at a time of national crisis following the Brexit vote.”

“We are ready to throw everything at building the Labour Party and the movement for a New Politics that Jeremy Corbyn leads.”

They expect a raft of heavyweights from across the Labour movement to attend, with a spokesperson from the group saying John McDonnell, Diane Abbott, Rebecca Long-Bailey, Angela Rayner, Paul Mason and Matt Wrack reported to be attending.

The group went on to say they expected more than three and a half thousand people to attend, with huge online interest in the event.

Matt Wrack, General Secretary of the FBU, who will be speaking at the rally this evening, said it was a “critical” time to support Corbyn

“If there was any right time to back the labour party leader, it is now. But it’s not just the right time – it is critical.

“Jeremy Corbyn has a long history of solid support for firefighters and the FBU, and he has pledged that if he came to power he would ensure investment in the service instead of cutting it to the bone. He is a committed trade unionist who holds very dear the value of workers’ rights and fairness in the workplace. To desert him now would be very short sighted. What happened to ‘Jez We Can’, and to the enormous feeling of optimism in this country when he became leader of the labour party?

“It is time to pull together, get behind the party’s elected leader and give him the support he needs to do the job he was appointed to do. I will be speaking tonight at the Momentum event and hope that this rally will galvanize party members into supporting the man they elected.”

Over 47,000 people have signed Momentum’s petition calling for unity and against a “manufactured” leadership contest since it’s launch on Saturday.

Support for Corbyn’s leadership is echoed across unions, with Len McCluskey writing that the leader is “better placed” to address Labour’s heartlands crisis then his moderate critics in the Guardian.