Labour would not win an early general election, Peter Mandelson has warned.

The former Labour cabinet minister said on Monday evening Jeremy Corbyn was presiding over a “policy vacuum”.

“We certainly haven’t got the programme or the planks of a manifesto coming together that people will vote for at the moment,” he said.

Lord Mandelson, who has been a longtime critic of Corbyn, was speaking at an event in London hosted by the Progress campaign group that is seen to be on the right of the party.

Asked how voters could be persuaded that there was an alternative to Theresa May’s Conservative Party, he said: “We have to engage in a process of policy inquiry, innovation and rebuilding which is all too absent in our party.

“Presently people are not being offered a viable alternative because the policy thinking simply isn’t taking place on the scale it should be.

“If we are going to be sufficiently equipped to fight and win the next general election, we have to come up with a darn sight better fist of ideas, policies and changes than are currently are being put out.

“There is a policy vacuum in the party and those who think it’s going to be alright on the day, and six months before a coming election we can just throw a manifesto together, a programme of policies that would be half credible, are mistaken.

“I am told the leadership of the party, and those working for the leadership, are working 24/7 preparing for an early general election. Well what are going to fight that election on?”

Lord Mandelson, a former EU trade commissioner who campaigned strongly for a ‘Remain’ vote at the referendum, also dismissed the idea he wanted Labour to take a more pro-EU stance simply for internal-party reasons.

“This isn’t a condemnation of Jeremy Corbyn,” he said. “And by the way. Those who think people like me are agitating over Brexit because we want to use to that issue to get at Jeremy Corbyn are completely wrong.

“People like me are agitating about Brexit because we care deeply about our country and the people we represent as a party.”

Last year Lord Mandelson famously told an audience he worked “every single day” to try and oust Corbyn. The comment triggered a backlash from supporters of the Labour leader.

Speaking on Monday evening, Lord Mandelson said as a result he now tried to follow a rule when speaking in public meetings not to generate headlines.

After delivering his critique of how the Labour Party was currently operating, he added: “There you are. I have broken my rule.”