The Labour party will on Monday outline six tests any Brexit deal will have to pass before the party can support it in a House of Commons vote.
Shadow Brexit secretary Sir Keir Starmer will also call on Theresa May to commit to introducing transitional arrangements to begin on March 29 2019, the expected exit date, until a "full and collaborative" EU-UK treaty can be agreed.
In a significant hardening of Labour's position, he will vow to reject any deal which does not meet the six tests.
The party's Brexit conditions are:
Does it deliver the "exact same benefits" as the UK currently has as a member of the single market and customs union?
Does it ensure a strong and collaborative future relationship with the EU?
Does it ensure the fair management of migration "in the interests of the economy and communities"?
Does it defend rights and protections and "prevent a race to the bottom"?
Does it protect national security and the UK's capacity to tackle cross-border crime?
Does it deliver for all regions and nations of the UK?
In a speech at Chatham House in central London, Sir Keir will back Mrs May's goal of a comprehensive free trade agreement but argue cooperation in security, science, research, culture and technology should also be retained.
He will warn against "increasingly powerful moves on the Government benches to sever our links with Europe", cautioning this "ideologically driven approach to Brexit would be disastrous and divisive".
"There is a worrying and increasingly powerful move on the Government benches to sever our links with Europe," he will say. "This is the authentic voice of the Brexiteers.
"Those who have argued for decades that exiting the EU offers a once in a generation chance for Britain to extricate herself from the entire European social and economic model: employment rights, environmental protections, fair corporate tax rates, investment in public services such as the NHS.
"Once a small minority in the Conservative Party, the Brexiteers are now in office and in power. This ideologically driven approach to Brexit would be disastrous and divisive."
Sir Keir will warn Mrs May against walking away from talks, which will begin after she triggers Article 50 of the EU treaties on Wednesday.
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The Prime Minister has insisted that no deal is better than a bad deal, but the Labour frontbencher will say: "The biggest danger currently facing British businesses, jobs and living standards is the chance of the Prime Minister exiting the EU without a deal.
"This is the worst of all possible outcomes. The Prime Minister should end this unnecessary uncertainty now by committing to establish appropriate transitional arrangements starting on March 29 2019 and lasting until a full and collaborative EU-UK treaty can be agreed".
On the six tests, he will say: "All of us want the best for Britain. But the stakes are high and the Prime Minister's approach so far does not bode well.
"Failure to meet the tests I have set out today will of course affect how Labour votes in the House of Commons.
"The Prime Minister should be under no illusion that Labour will not support a deal that fails to reflect core British values and the six tests I have set out today."
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