Jeremy Corbyn is facing calls to commit a Labour government to keeping Britain in the single market after it leaves the European Union.

More than Labour 30 MPs and 11 MEPs – as well as other senior party figures – have signed up to a statement warning that leaving the single market would leave working people worse off and make it harder to reverse Conservative austerity.

Signatories to the statement, posted on the opinion section of The Guardian website, include Chuka Umunna, Maria Eagle, Liz Kendall, Stella Creasy, Chris Bryant, Pat McFadden and Ben Bradshaw. Shadow ministers Andy Slaughter, Daniel Zeichner and Ruth Cadbury, as well as Thangam Debbonaire, an opposition whip, have also signed.

Read our manifesto to find out what a fresh start with a Labour government will look like ↓ https://t.co/YeRUNSwNVq — The Labour Party (@UKLabour) May 18, 2017

The Labour election manifesto – which commits the party to honouring the outcome of last year’s referendum vote to leave the EU – calls for a “strong emphasis on retaining the benefits of the single market”.

However, the statement argues that it is possible for Britain to remain a member of the single market without being a member of the EU.

“We must be clear – ‘access’ to the European single market is both different and inferior to ‘membership’ of the single market,” it said.

“Why? Because if we leave the single market, whatever the level of access is negotiated, working people across Britain will be worse off and revenue to the exchequer will plummet – revenue the next Labour government will need to bring an end to years of damaging Tory austerity.”

Chuka Umunna is among the signatories (Victoria Jones/PA)

The statement said that on the Conservative side the charge to “junk” Britain’s membership of the single market was being led by a “motley crew of hard-right, pro-Brexit Tories” – including Michael Gove, Boris Johnson and Iain Duncan Smith – who wanted to roll back the social protections it delivered.

“The single market is not a simple free trade zone.

“It is, uniquely, a framework of rules that protects people from the worst excesses of globalisation and unfettered capitalism, in addition to easing trade across the continent,” it said.

“If we have mere access to the single market, we are talking about leaving this framework of rules and achieving mere reductions in tariffs for trade with the European Union.”