Labour will push the government to secure access, rather than membership, of the EU's single-market, John McDonnell confirmed this morning (26 September).
The shadow chancellor, speaking ahead of his address to Labour's annual conference in Liverpool, also attacked Prime Minister Theresa May for not being "in the game at all".
"We want access to the single-market. We want the best deal that we can get," he told BBC Radio 4's Today programme.
"The problem that we've got is that the government doesn't seem to have a strategy, there was no fall-back position prepared by David Cameron and Theresa May hasn't been in the game at all.
"There's been no real development of strategy and they've alienated possible partners in Europe that could have helped us in terms of developing a proper relationship for the future."
McDonnell's comments come after Jeremy Corbyn, who was re-elected Labour leader on Saturday, said he opposed a so called "hard-Brexit", which would see the UK just sign up to World Trade Organisation (WTO) rules.
Speaking in July, the shadow chancellor warned against the damage done to the British economy by "pulling out of the single market".
He added: "Whatever emerges from negotiations, when the final proposals for Brexit are decided, we do not want to lose the benefits that membership of the European Union has brought."
Emily Thornberry, the shadow foreign and Brexit secretary, told Sky News' Murnaghan show earlier this month that access to the single-market of 500 million people would be "really important" to Labour.
"There are some of the regulations around the free market that we have always had questions about and we continue to question and that must be part of the negotiations, so, for example, we are concerned that it could be an interpretation of some of the regulations that we wouldn't be able to renationalise the railways, we think that is something that it isn't for Europe to decide, it's something for the British to decide."
Thornberry also said Labour wanted "realistic and workable controls" on migration, alongside access to the single-market.
But EU chiefs, including European Parliament President Martin Schulz, have said that the UK cannot have "single market àla carte", which would include immigration reforms and single-market access.
The prime minister has ruled out triggering Article 50 of the Lisbon Treaty, the official mechanism to split from the EU, this year. But it is expected the government will make the move sometime next year, followed by two years of negotiations with Brussels.
UPDATE: 11:15 BST
Susan Kramer, the Liberal Democrat's Treasury spokesperson, said: "McDonnell is unwilling to fight for Britain's place in the Single Market.
"Instead of talking about the existential threat Brexit poses to British businesses, he is content to make ludicrous claims that we no longer need the free market.
"Businesses don't want an economy where John McDonnell decides what's good or bad - they want someone who will fight for membership of the Single Market, the world's largest trading bloc.
"The Shadow Chancellor's speech today shows that Labour under Corbyn has no interest in tackling the real issues facing our economy today."