Len McCluskey, who is general secretary of Unite, which provides Jeremy Corbyn’s party with massive financial backing, warned a second vote could cause significant damage to the party with its traditional supporters. He also claimed some Labour “advocates” were trying to deny Mr Corbyn a general election victory by continuing the debate on the issue. Writing in The New Statesman, Mr McCluskey said it was important for Labour to begin building a coalition with other parties on what he termed a modified Brexit deal.
Mr McCluskey acknowledged the “clear possibility” of a second vote.
However, he added: “Better by far that parliament can agree a deal, acceptable to the European Union, which can command a broad base of support both among the 52 percent who voted Leave and those in the 48 percent who accept that democratic verdict.”
He advised Mr Corbyn to accept a deal which would include a permanent custom union, guarantees on workers’ rights and environmental protections, as well as close alignment with the single market and a “lasting solution” on the Irish border question.
Mr McCluskey suggested most MPs would back a “pragmatic resolution to what is fast becoming a national agony”.
At its annual conference earlier this year, Labour agreed to consider a second referendum alongside other options if it was unable to force a general election.
But Mr McCluskey backed Mr Corbyn’s refusal to call a vote of no confidence in Theresa Mays government so far, branding it a “box what some retainers wished to tick on their way to another referendum”.
MPs are due to vote on Mrs May’s Brexit plan in three weeks.
Mr McCluskey has said Labour needed to carry seats in both Remain-backing Londona and Scotland, and Leave-leaning constituencies in the Midlands and the north in order to gain the Parliamentary majority required to put Mr Corbyn in Number 10.
He added: “There could be nothing better designed to blow that alliance apart than second referendum, as things stand.
“The idea that we spend months visiting Mansfield and Middlesbrough telling people they made a stupid mistake is a deeply unappealing one.”
In a swipe at Labour politicians campaigning for a second vote, he claimed for some within the party “endangering the prospects of a Corbyn government would not only be a price worth paying for Britain staying in the EU, it would be a win-win.”
His words may have been aimed at party colleagues such as Chuka Umunna, a fervent Remainer and advocate of a second vote, as well as ex-Prime Minister Tony Blair.
Speaking earlier this week, Mr Blair told euronews.com: “What leaders were saying to me when I started having this conversation a year ago, they would say to me ‘yeah but it’s never going to happen, another referendum’.
“I think the mood has changed in the last couple of months.
“And now people are saying ‘well could it really happen?’
“I need to get the European leaders to the next stage which is to realise that the probability is it’s going to happen.”