The lawmakers called on May to set out the broad outlines of her plan before triggering Article 50 of the European Union treaty, which will start the formal process of negotiating Britain's exit from the bloc.
Doing so, which has also been mooted by Brexit Secretary David Davis, would allow the United Kingdom to have a soft Brexit, rather than a "hard" one which would involve leaving the free trade area.
That was a reaction to comments from chancellor Philip Hammond, who had suggested there are "conversations within government" about changing the position.
"What I will say [and] this is very important and people will want to hear this: I do believe that as a result of Brexit, we will be able to take back control of the money that we now give to Brussels".
"I think it's of massive benefit to this country that we are open".
May is facing a rocky time less than four months before the deadline she has set herself for triggering two years of divorce talks with the EU.
"They do not want the Conservative party to be Ukip-lite, nor to hear that their desire for a negotiated Brexit.is somehow an attempt to delay or simply an expression of Remoaning".
Critics say leaving the single market would be an "act of self-harm".
If the Supreme Court does rule against the government, May will file legislation just 16 words long to reduce the chances of it being amended, the Sunday Telegraph said.
"What the European Union wants to achieve is a partnership", he said.
Attorney General Dominic Grieve is among a group of Conservatives warning Theresa May that she risks losing the next general election if she alienates moderate Conservative voters by pushing through a "hard Brexit".
"In 180 days your government starts these negotiations", Starmer said, sitting next to Johnson in the television studio.
"If they want to do that fine".
"We are not some bit-part or spear-carrier on the world stage". By contrast, Mike Rake, chairman of BT Group Plc, told ITV that it's "critical" any deal allows the most access possible to the single market and for foreign labor to enter Britain.
"There will be more sturm und drang (storm and stress) between now and the end of the negotiations and it may get pretty hairy at times and there may be some hard bits but beneath it all there is a massive fondness for the United Kingdom and the desire to do the best possible deal".