Theresa May is set to meet trade union chiefs in Westminster on Thursday as part of her latest desperate bid to woo them to support her Brexit plan.
TUC general secretary Frances O'Grady, Len McCluskey of Unite, Dave Prentis of Unison and Tim Roache of the GMB will all hold separate meetings in Whitehall.
The discussions are part of Mrs May's bid to get political backing for a Brexit agenda which would command a majority in the Commons after her plans were humiliatingly rejected by MPs last week.
Downing Street said she will be discussing employment rights, environmental standards “and those sorts of things”.
Despite Jeremy Corbyn branding the talks a "stunt", a senior spokesman said the Labour leader's request for the party's MPs to boycott discussions with Mrs May did not extend to union leaders.
The spokesman said: "Of course it is absolutely right for union leaders to represent their members and to engage with the Government on issues that affect their members.”
But he warned: “There must be a majority in Parliament for any deal, including a mechanism to rule out no-deal.”
A Downing Street spokesman said: "The Prime Minister has said that this is a process of engagement across the House of Commons but also with other interested sectors.
"She has spoken to business leaders and she will be talking with union leaders.
Unions have been warning of the impact on jobs of a no-deal Brexit and have been pressing for assurances about employment rights after the UK leaves the EU.
Some have also argued in favour of a second referendum.
Thursday’s meetings come as there appeared to be growing support in Labour ranks for a bid by backbencher Yvette Cooper to extend Article 50 – which would keep the UK in the EU longer – unless a deal is reached by the end of February.
Ms Cooper's bid, which has cross-party backing including from Conservative Nick Boles, is one of a number of amendments that could be voted on Tuesday if selected by Commons speaker John Bercow.
Meanwhile, in another sign of opposition to the Prime Minister's stance, 19 ministers, including Cabinet members, have reportedly been meeting to discuss preventing a no-deal Brexit.
One member of the ministerial group dubbed it the "hair-shirt club", the Daily Telegraph reported.
Additional reporting by Press Association.
