WORKING-CLASS voters could be hoovered up by a Syriza-style anti-austerity party if Labour continues to promote the EU’s capitalist agenda, party grandees warned today.

The party’s biggest individual donor John Mills said there was still an “evident danger” of Labour shedding more of its core vote in spite of its “very welcome” U-turn to supporting a referendum on EU membership. He said the party’s current stance would “weaken Britain’s hand” in negotiations.

And in an exclusive article in today’s Morning Star, left MP Kelvin Hopkins issues a stark warning over the “virtual disappearance” of Greek centre-left party Pasok following its “deadly embrace” with right-wingers in support of EU austerity.

The interventions come after anti-Establishment parties made huge gains in local elections in Spain, which, like Greece, has seen bitter opposition to austerity policies imposed by the “troika” of the European Commission, the European Central Bank and the International Monetary Fund.

Analysis by Labour MP John Healey has revealed that Ukip’s share of the vote was higher in Labour-held seats than in Tory ones. Asked if a party more akin to Greece’s Syriza or Spain’s Podemos could suck up disillusioned Labour supporters from the left, Mr Mills said: “There is a risk.

“It was very clear [prior to the election] that most people did want a referendum and that many wanted to come out of the EU. They should have a chance to express their view.

“What’s going to happen now is that the Labour Party will say it supports a referendum, but a very large proportion of the party will campaign to stay in. This will weaken Britain’s hands in the negotiations — you can’t go in saying whatever happens you’ll accept it.

“That won’t go down well with the British people.”

He said a “much more robust attitude to negotiations” was required and that it would be preferable for Labour to state that it would “judge [its position] when we see what the outcome is.”

Mr Hopkins hails the vindication of leftwingers who recognised the “anti-socialist and anti-democratic nature of the EU” at the time of its establishment and Britain’s entry.

“The reactionary Thatcherite revolution inflicted on Britain has pushed the neoliberal agenda far beyond that of Continental Europe, but the direction and objectives are the same,” he said.

“However, on the Continent, it is fear of the likely political reaction by millions of workers which has held back the neoliberal thrust.

“The whole EU economic strategy has proved a failure and while a useful level of co-operation between economies on a voluntary and mutually beneficial basis is appropriate, bureaucratic control and economic dictats from the EU institutions do not work.”

Britain’s referendum on EU membership is timetabled to take place towards the end of 2017.