Britain would be reduced to a "colony" of Brussels by Labour's plans for a post-Brexit customs union with the EU, Foreign Secretary Boris Johnson has said.
The Cabinet heavyweight accused Jeremy Corbyn of raising a "white flag" on Brexit in order to try to defeat the Government in an upcoming Commons vote on remaining in a customs union.
Mr Johnson tweeted: "Crumbling Corbyn betrays Leave voters - and all because he wants to win a commons vote. Cynical and deluded."
The Foreign Secretary added: "Corbyn's Brexit plan would leave U.K. a colony of the EU - unable to take back control of our borders or our trade policy. White flag from labour before talks even begin."
International Trade Secretary Liam Fox said Mr Corbyn was seeking to frustrate Brexit.
He said: "This is a cynical attempt by Labour to try and frustrate the Brexit process and play politics with our country's future - all the while, betraying millions of Labour voters.
"Labour's confused policy would be bad for jobs and wages, it would leave us unable to sign up to comprehensive free trade deals, and it doesn't respect the result of the referendum."
However, Tory former chancellor George Osborne made it clear he believed Mr Corbyn had seized the political initiative.
Now editor of the London Evening Standard, he tweeted that the newspaper's editorial said: "Tories gifted Corbyn an open goal on the customs union, and he just put the ball in."
The DUP's Sammy Wilson accused Labour of "cheap political opportunism" in attempting to try to bring the Government down with a customs union vote in the Commons.
Mr Wilson said the DUP would continue to back Prime Minister Theresa May on Brexit.
"It is clear that Jeremy Corbyn's speech today is driven by cheap political opportunism, completely overturns previous promises made by the Labour Party during the last general election that it was opposed to membership of the customs union and is a blatant attempt to bring down the Government rather than safeguard the interests of the UK or workers in industries across the United Kingdom who would benefit from the United Kingdom's freedom to make its own trade deals outside a customs union," he said.
"Corbyn is hoping to capitalise on the opposition to leaving the EU from the few malcontents in the Conservative Party. He clearly hopes that they will join with him, putting personal prejudices ahead of their own party duties.
"The DUP, as we have done already, will be giving our full support to the Government to oppose this Brexit-wrecking policy which, regardless of the promises made by Corbyn, will result in the UK still being tied to regulations, directives and diktats from the EU."
The Liberal Democrats accused the Labour leader of only "slight" movement on his EU withdrawal stance.
The party's Brexit spokesman, Tom Brake, said: "Corbyn started his speech claiming that Labour's position on Brexit has been consistent, by which he must mean consistently vague. And today was no different.
"His slight movement on the customs union and some EU agencies might be one step on the road to rationality, but there is still a long way to go before the rhetoric meets reality. The Labour leader spoke of putting the British people first, but made no guarantees on making sure they are the ones who have a final say on the Brexit deal."
Green Party co-leader Caroline Lucas tweeted: "Freedom of movement does NOT have to end if we leave the EU. Norway has freedom of movement. Wish @jeremycorbyn would stop repeating this myth."