Theresa May has been urged to “face down” the Brexiteers by Sir Keir Starmer as he set out Labour’s six tests for the imminent negotiations with the European Union.

Sir Keir, the shadow Brexit Secretary, also reiterated Jeremy Corbyn’s suggestion that Labour would not support any final Brexit deal unless it delivers the “exact same benefits” the UK currently enjoys within the EU.

In a speech at Chatham House in central London, Sir Keir warned against the “increasingly powerful move on the Government benches to sever our links with Europe” and cautioned against an ideological exit from the EU driven by Brexiteers, which would “be disastrous and divisive”.

It comes as the Prime Minister prepares to invoke Article 50 of the Lisbon Treaty on Wednesday, starting Britain’s two-year countdown for exiting the EU.

Anticipating splits in the party during the two-year negotiation phase, he continued: “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. And it would stand as a road block to continued cooperation in the important fields of technology, research, medicine, security, science, arts and culture.

Labour’s six tests 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?

“The Prime Minister needs to face down these Brexiteers who would distance us from Europe.”

Ahead of her bilateral meeting with the Scottish First Minister Nicola Sturgeon on Monday, Sir Keir also added that Ms May’s failure to engage with the Scottish Government had “provided an excuse for the SNP to press ahead” with a second independence referendum.

“This is, I fear, becoming the defining characteristic of the way the Prime Minister is conducting the process – guarded, closed, unable to build a consensus or form alliances,” he added.

“Instead of being open and willing to listen on differing views and incredibly complex issues, she’s retreated into government by mantra – ‘Brexit means Brexit’, ‘No running commentary’, ‘No deal is better than a bad deal’; bland phrases designed to shut out dialogue.”