Jeremy Corbyn has lashed out at the eight ex-Labour MPs who defected from the party, declaring them part of an “establishment coalition” which backs Tory austerity, corporate tax cuts and privatisation.

In a sharp counter-blast at those who have joined the breakaway Independent Group in the Commons, the Labour leader’s spokesman suggested they supported “failed” policies from the Conservatives’ and Tony Blair-era.

The spokesman said that Corbyn “regretted” the departure of the eight MPs, who quit this week over anti-semitism and fears that Labour would fail to support a second referendum on Brexit.

But in words clearly authorised by the leadership, he said that it was clear that the defectors – Chuka Umunna, Luciana Berger, Angela Smith, Chris Leslie, Mike Gapes, Ann Coffey, Gavin Shuker and Joan Ryan – had a policy agenda that differed from Labour’s new membership.

“The fact is they have formed what is effectively an establishment coalition based on the failed and rejected policies of the past, austerity corporate tax cuts, privatisation,” the spokesman said.

“It’s precisely because those policies were seen to have failed and were rejected that the direction under the Labour party has changed since Jeremy was elected. And we demonstrated at the general election that a different approach has mass electoral appeal.”

When challenged on where such policies were outlined, the spokesman said they were “at their launch yesterday”.

“At the event they were clearly identified with Chris Leslie but others too, with policies which are clearly of the past, the policies of business-as-usual,” he added.

The party leadership also defended new plans to force defecting MPs into quitting Parliament to fight by-elections.

Deputy leader Tom Watson described as “spiteful” proposals outlined by Labour’s shadow cabinet office minister Jon Trickett to make MPs who switch parties face the electorate if 10% of voters demanded a new poll.

But Corbyn’s spokesman said that the plans had been “agreed by the leadership”, even if not agreed explicitly by the shadow cabinet.

Leslie hit back at the attack, telling HuffPost UK that the Independent Group of MPs believed Brexit would be a driver of more austerity.

“The parties that enable Brexit will be the pro-austerity parties because the revenues that we lose will hit our public services. I’m going to make it my job to hold those facilitate that to account for the cuts that come,” he said.

On privatisation, the former Labour MP added: “If anything I think there’s a good case for mutualisation of services.

“Would I question mass renationalisation or mass nationalisation? Yes I would because is £90bn buying shares of a water company better value than £90bn on affordable housing?

“You could get 750,000 affordable homes for that amount of money. My priorities would be different, but that’s not being pro-privatisation.

“We haven’t got a suite of policies because it’s 48 hours since we started, what we have are a set of values. There are people in Britain who are pro-markets, laissez-faire, there are people who are pro-statist, command-and-control. I’m in favour of regulated markets and government action and intervention where appropriate, led by evidence not by ideology. I think the mainstream British public get that.”

However, the Labour leadership’s response echoed that of the grassroots organisation, Momentum, which was founded to embed Corbyn’s political direction after his two landslide leadership elections.

Momentum’s National Coordinator Laura Parker said: “It’s clear that the new party is a Blairite-Tory coalition aimed at resurrecting a dead agenda of privatisation, deregulation and tax cuts for the super rich.

“This is not what their constituents voted for. Umunna, Leslie and Smith’s constituents overwhelmingly voted Labour and have ended up with an MP in coalition with the Tories.

“This is unfair, undemocratic and dishonest. The only decent thing to do is to call a by-election and let their constituents decide.”