JEREMY Corbyn is being urged to attend a new year summit to help draw up cross-party parliamentary plans to remain in the European single market and customs union.

The call is being made by the SNP’s Ian Blackford, who has written to the UK Labour boss and leaders of the other opposition parties in the hope of furthering efforts to avoid a hard Brexit. It comes as the Conservative Government is poised for the second phase of talks with the EU, where the focus will be on what sort of trade relationship will exist once the UK has left the bloc.

As he published his letter to party chiefs, the SNP’s leader at Westminster said it is vital parties work together to safeguard single-market membership as a means of protecting jobs, workers’ rights and living standards. Blackford said: “Extreme Tory Brexit plans to drag Scotland and the UK out of the single market would cause catastrophic damage to the economy – costing hundreds of thousands of jobs, and hitting people’s incomes, livelihoods and living standards for decades to come.”

“It is time for MPs of all parties to put politics aside and work together, in the national interest, to protect our place in the single market and customs union. Short of retaining our EU membership, that is by far the least damaging option, the best compromise, and the only way to protect jobs, incomes, and workers’ rights.”

Theresa May has repeatedly said the UK will leave both the single market and customs union at the end of March 2019.

During a temporary transition period, which will last until the end of 2020, the UK will continue to be in both, and under the jurisdiction of the European Court of Justice. The SNP, Liberal Democrats, Plaid Cymru, and the Green Party are all committed to remaining in the single market and customs union, but Labour’s position is less clear.

Despite most Labour members, and many of the party’s MPs, MSPs and councillors, supporting single-market membership Corbyn has refused to back this position, saying it could prevent state aid and encourage privatisation. He has said he wants “tariff-free trade access to the European market”.

The SNP believe a Commons majority to protect Scotland and the UK’s membership could be secured if Labour gets behind cross-party efforts, and if soft Brexit Tories come on board. Blackford has invited Corbyn and the other opposition leaders, including Caroline Lucas of the Greens and Vince Cable of the LibDems, to the summit in the Commons on January 8.

Blackford highlighted a parliamentary vote earlier this month on the Brexit Bill, which saw the UK Government defeated after a rebellion by 11 Tories, with MPs backing an amendment which gives a legal guarantee of a vote on the final Brexit deal struck with Brussels. Blackford added: “As we saw with the successful amendments to the EU Withdrawal Bill, when opposition parties work together effectively it is possible to sec- ure a parliamentary majority and deliver change in the national interest.

“Those who say they care about people’s jobs and incomes must now look at the evidence, look at their consciences, and get behind cross-party efforts. Anyone who stays on the fence, and allows dogmatic Brexiteers to drag us out of the single market, will bear equal responsibility when people’s jobs are lost and their incomes are slashed.

“More than ever the UK desperately needs strong leadership and straight talking, honest politics – that is what the SNP will continue to provide as we focus our efforts on retaining our place in the single market to protect our economy and safeguard jobs.”

In his letter to the fellow opposition party leaders Blackford cited analysis from the Fraser of Allander Institute which revealed leaving the single market would put at risk up to 80,000 jobs and cost £2000 per person in Scotland every year.

He also referred to comments from trade union leaders who have argued the UK needs to stay in the single market to guarantees that workers’ rights will be protected.

Last week it emerged May was considering ditching the European working time directive, which protects employees from working excessive hours, once the UK had quit the EU.

The Scottish spokesperson for the Liberal Democrats Christine Jardine MP said: “There is growing evidence that people across the UK want to have the opportunity to reject a bad deal on Brexit. Leaving the single market would undoubtedly be a bad deal.

“Liberal Democrats will work constructively with all those who want the UK to stay in the single market. With thousands of jobs at stake, it is important that efforts are made across the parties to retain the benefits of the single market."

Labour did not respond last night to a request for a comment.