Theresa May was defiant in the face of defeat today, as she readies for another showdown between the government and backbench Tory rebels.

Last night the Lords again voted in favour of giving parliament a meaningful vote on the final Brexit deal, returning the amendment to the Commons for MPs to vote once again in a process known as ping-pong.

But the Prime Minister's spokesman insisted there would be no change in the government's stance that any amendment must pass the three tests set out by Brexit secretary David Davis- that it must not undermine the negotiations, change the constitutional role of parliament and government in negotiating international treaties, and respect the referendum result.

He added: "We cannot accept the amendment on meaningful vote agreed in the Lords. Agreeing to amendable motions would allow parliament to direct government on its approach to exiting the European Union, binding the Prime Ministers hands and making it harder to secure a good deal for the UK… The original amendment struck the right balance between respecting the tests set out by government as well as delivering on the aims of Dominic Grieves own amendment

"That is why we will be tabling original amendment today and will look to overturn the Lords' decision tomorrow."

Asked if the Prime Minister would be speaking with the rebels, the spokesman said May "speaks with her colleagues all the time".

But backbenchers are preparing for a showdown.

Phillip Lee, who resigned his post as a junior justice minister last week, tweeted: "I will be voting for that same amendment in the House of Commons and urge all my colleagues to do likewise. MPs cant stand up for the people they are elected to represent unless parliament has a voice."

Dominic Grieve, the former attorney general whose amendment is at the centre of the row, this morning insisted it was "complete nonsense" to suggest it would bring down May's government.

"This is the end stage of the consideration of the details of a piece of legislation," he said. "Whichever way the vote ultimately goes, the idea that the government is going to be endangered by this difference of view within the House of Commons, which might lead to its defeat, is complete nonsense.

Although he declined to give a figure of who would back him tomorrow, Grieve – who has abstained on his own amendment previously – told Sky News there was support among those who "rationally" see it as "better than a road crash" which would come about from a no deal.