Len McCluskey will use his 'influence' to campaign for new Brexit referendum if Unite members want one

Campaigners believe support of Unite boss could be crucial in persuading Jeremy Corbyn to back a fresh vote

Len McCluskey said he believed Unite members would stand by its existing policy, to ‘leave the option open’ (PA)

Len McCluskey has pledged to campaign for a fresh Brexit referendum with “all of the influence and power of oratory that I have” if his Unite members back the move.

Members of Britain’s biggest trade union will decide on Tuesday whether to abandon its current opposition to a public vote on Theresa May’s deal.

At the weekend, a poll found that 57 per cent of Unite members did support a further referendum, with just 34 per cent opposed to the idea.

Campaigners believe the support of the general secretary of Unite – Labour’s biggest funder, with more than 1.4 million members – could be crucial in persuading Jeremy Corbyn to back another vote.

Speaking ahead of his members’ decision, Mr McCluskey said he believed they would stick to Unite’s existing policy, which is to “leave the option open”.

But he vowed: “Whatever decision is taken tomorrow by our members, here at our policy conference, that becomes Unite policy.

“I will use all of the influence and power of oratory that I have to promote that policy, but I don’t want to rush ahead of the debate.”

Asked if the Unite leadership would allow a “clear vote” by its members, Mr McCluskey replied: “Absolutely. The way our union operates, like any union, is highly democratic.”

And he added: “I’m conscious that Jeremy Corbyn has not ruled out the option of moving to a people’s vote if, in the end, the political climate requires it.”

According to the YouGov poll, by the People’s Vote campaign, 49 per cent of Unite members want their union to push for a further referendum, with 39 per cent opposed.

The members polled also believed that Britain would be economically worse off if it left the single market after Brexit, by a margin of 58 per cent to 21 per cent.

That separate controversy – with both Unite and Labour also opposed to single market membership – is likely to be the subject of a second vote on Tuesday.

Mr McCluskey added: “It’s our policy to respect the result of the referendum but to have serious negotiations with the EU to gain a customs union and access to the single market to protect jobs in this country.”

The Unite boss is also using his union’s conference to push for Labour to focus on reconnecting with the party’s blue-collar voters in the North.

He said Labour could forget about winning power unless it addressed the concerns of natural supporters in places such as Mansfield and Middlesbrough.

“We all know that the next election is far from in the bag,” he told the conference.

“One problem is a weakness in some industrial areas outside the big cities, among older working-class voters in particular. Extra seats in London are not going to get Jeremy Corbyn into Downing Street.

“So, test every policy against how it is going to play in Walsall and Wakefield, Mansfield and Middlesbrough, Glasgow and Gateshead.”