Continued membership of the European Union single market is the best way to protect British workers after Brexit, the TUC’s general secretary, Frances O’Grady, will say on Monday, increasing the pressure on Jeremy Corbyn to shift Labour’s policy.

Speaking at the TUC’s annual congress in Brighton, as MPs in Westminster prepare for a debate on the EU withdrawal bill, O’Grady will say: “We have set out our tests for the Brexit deal working people need. Staying in the single market and customs union would deliver it.”

Her speech comes after the TUC’s general council, which represents about 50 trade union organisations, officially stated that it was in favour of remaining in the single market after a meeting on Thursday.

On Sunday night the Brexit secretary, David Davis, urged MPs not to vote for “a chaotic exit from the European Union” ahead of a vote on the repeal bill on Monday. “The British people did not vote for confusion and neither should parliament,” he said.

Corbyn and the shadow Brexit secretary, Keir Starmer, recently announced Labour would back continuing membership of the EU single market and customs union for a transitional period, which should last as long as it takes to strike a new trade deal.

Since that announcement, Corbyn’s spokesman has stressed the disadvantages of the single market – including state aid rules which Labour believes prevent governments from rescuing ailing businesses; and procurement rules preventing them favouring domestic firms.

But unions are a key support base for Corbyn’s leadership and have become increasingly vocal about the risks of plunging out of the single market.

Some of his party’s backbenchers, including former shadow health secretary Heidi Alexander and Progress chair Alison McGovern, have set up a “Labour campaign for the single market” in a bid to influence the party’s policy.

In her keynote speech in Brighton, O’Grady is expected to say: “The prime minister is sticking to the same old script that she can get whatever she wants, that we can all have all the same benefits of the single market without playing by the rules.

“This isn’t a grown-up negotiating position. It’s a letter to Santa. My challenge to all political parties is this: when it comes to Brexit, don’t box yourselves in. Don’t rule anything out. Keep all options on the table. And put jobs, rights and livelihoods first.”

She will be speaking as Theresa May gears up for her toughest parliamentary challenge since her majority was wiped out in June’s general election.

On Monday, a second day of debate in Westminster on the EU withdrawal bill is being held, followed by a series of tough late-night votes, expected after midnight, with Corbyn imposing a three-line whip on his MPs to reject legislation he regards as a power-grab.

The bill will allow the government to transpose EU law on to the UK statute book, but critics say it places too much power in the hands of ministers to make sweeping changes in the process.

Davis said in a statement released on Sunday night: “A vote against this bill is a vote for a chaotic exit from the European Union. The British people did not vote for confusion and neither should parliament.”

May is expecting to scrape through the votes on Monday, because senior Tories who have expressed concerns about the bill, including Dominic Grieve and Anna Soubry, are expected to hold their fire until the committee stage later in the autumn, when Davis has signalled he will be willing to listen to amendments.

The prime minister will face a series of further challenges in parliament later in the week over the Conservatives’ bid to pack crucial Commons committeesand a Labour motion aimed at lifting the pay cap for public sector workers, an issue that has become increasingly controversial.

The EU withdrawal bill is one of seven pieces of legislation the government has said it needs to pass to facilitate Brexit by the end of this two-year session of parliament.

Tony Blair appears on the Andrew Marr Show. Photograph: Getty Images

On Sunday, Tony Blair urged MPs to speak out against Brexit if they had doubts about it. “Brexit is a distraction, not a solution, to the problems this country faces,” said the former prime minister. “If members of parliament really believe that, then their obligation is to set out solutions that deal with the actual communities and problems people have, and not do Brexit which is actually going to distract us from those solutions.”

In the first of a series of interventions he plans this autumn as Brexit talks intensify, Blair’s Institute for Global Change published a paper setting out a series of ways in which the UK could restrict immigration within existing EU free movement rules.

Speaking on BBC1’s Andrew Marr Show, Blair said: “If, for example, the anxiety is downward pressure on wages as a result of an influx of EU migrants coming and doing work, say in the construction industry, we have it within our power to deal with that through domestic legislation.”



He suggested the mood within the EU on the meaning of free movement was changing, with the French president, Emmanuel Macron, backing a directive that would crack down on using migrants to undercut the wages of domestic workers.

“If we want to deal with those questions, we can deal with them without the sledgehammer that through Brexit destroys the EU migration that we’ll actually need,” he said.