Jeremy Corbyn was empty-chaired at a cross-party summit on fighting hard Brexit.
The Labour leader was invited to a meeting of Opposition leaders who want to see Britain stay inside the single market and customs union - but he rejected their invitation, with the party saying the summit was a “political gimmick”.
The leaders argue Prime Minister Theresa May is steering the country towards an exit that will hit jobs and the economy.
SNP Westminster Leader Ian Blackford - who previously criticised Corbyn for a “pathetic” lack of leadership on Brexit and has pointed out that 87% of Labour members support single market membership - released a joint statement with the leaders of the Lib Dems, the Green Party, and Plaid Cymru after the meeting in Parliament on Monday.
It is not Labour Party policy to remain in the single market beyond a transition period post-Brexit and Corbyn says fighting to remain in it is “based on a flawed assumption”.
A statement from Blackford, Lib Dem leader Vince Cable, the Greens’ Caroline Lucas, and Plaid Cymru Westminster leader Liz Saville-Roberts says: “Leaving the single market will cost jobs.
“Over three million UK jobs are linked to trade with the EU - one in every ten jobs. There is no such thing as a ‘jobs-first’ Brexit that includes terminating our single market membership – these outcomes are incompatible.”
It adds: “Today, we call on the Prime Minister to dismiss any chance of a ‘no deal’ scenario. The possibility must be firmly off the table.
“We will work together in the Commons alongside Members from all political parties to protect the UK economy and prevent any attempts to drag Scotland, England, Wales and Northern Ireland out the single market.
“Moving forward together, we will seek to meet with key stakeholders, such as the TUC and business groups, and the devolved administrations including the London Assembly, to express Parliament’s cross-party desire to avoid the damage that Brexit will cause, and encourage all efforts to avoid such an outcome.”
Corbyn replied to a letter from Blackford asking him to attend.
A Labour Party spokesperson said: “This publicity-seeking meeting is little more than a political gimmick.
“As Jeremy said in his letter, the proposed meeting appears to be based on the flawed assumption that the Single Market is a membership club that can be joined. It is not.
“We have consistently said that we are committed to negotiating to keep the benefits of the Single Market and securing the best possible deal for the whole of Britain, which protects our economy and the people of this country, whilst at the same time respecting the result of the referendum.”