Last ditch talks were taking place in Brussels on Sunday in what government sources called a “final throw of the dice” by negotiators.
With the transition period set to end on December 31, time is running out and both the European and UK parliaments must ratify any agreement Boris Johnson signs off.
Keir Starmer is said to favour whipping Labour MPs to back a deal should one come before the Commons, but his shadow ministers on Sunday would not rule out the party abstaining amid internal divisions on the issue.
Some pro-Remain MPs and members of the shadow cabinet have been reported as vehemently opposed to vote for an agreement.
Unite general secretary McCluskey has now intervened, warning Starmer he needs to “win the trust of the red wall seats” after the 2019 general election result.
He told Times Radio he expects a deal to go through parliament, adding: “Frankly, Labour need – on the most important issue of the day – not to be seen to be sitting on the fence.
“The idea of an abstention, to me, would be completely wrong. I hope they’ve learnt the lesson back in December that any confusion over this will be damaging to them.”
Pressed if Labour should not abstain but vote for a deal, McCluskey replied: “Yes, in my opinion let’s get Brexit done and out the way, it won’t stop us being critical if indeed the deal gives us all kinds of issues and problems going forward.”
McCluskey also said Johnson must avoid crashing the UK our of Europe without a deal, adding: “On the other hand if it’s a thin deal, which I suspect it will be, if indeed we get a deal, he needs to also be in a position in six months if things are going wrong to be able to attack the government without then being regarded a hypocrite because he voted for the deal.”
Speaking to Sky News on Sunday, shadow home secretary Nick Thomas-Symonds could not rule out the party abstaining, however.
If @NickTorfaen says leaving the EU without a deal would be "catastrophic" surely Labour will vote for a deal? @SophyRidgeSky
"It's the responsible thing to actually consider the deal that is agreed" says the Shadow Home Secretary.#Ridge https://t.co/Y7JlOUGQ4W pic.twitter.com/SXcFCpd4O6
— Sophy Ridge on Sunday (@RidgeOnSunday) December 6, 2020
Such a move is unlikely the result, given Johnson has a majority of 80.
Thomas-Symonds said: “On the issue of the Brexit trade deal, potential trade deal, my first message is this: we absolutely need to get a deal.”
He added: “In terms of our position on any deal, clearly we need to see what has been agreed, I think that’s a sensible, responsible position to take but we very much hope there is a deal because there seem to be two paths before us at the moment, a path of leaving the transition without a deal and leaving with a deal and we do know how catastrophic the no-deal outcome would be.”
When pressed by presenter Sophy Ridge on what position the party should take, he said “there are various options, when you get any particular vote that you get before parliament there are options” but that “the responsible thing is that first of all we need to get a deal, then consider what has been agreed”.
This article originally appeared on HuffPost UK and has been updated.