LIVERPOOL, England (Reuters) - Britain’s main opposition Labour Party is preparing to vote against any deal Prime Minister Theresa May clinches with the EU as it is increasingly unlikely to meet the tests Labour has set out, its Brexit spokesman Keir Starmer will say on Tuesday.

The Labour Party's Shadow Secretary of State for Departing the European Union Keir Starmer speaks to journalists at his party's conference in Liverpool, Britain, September 25, 2018. REUTERS/Hannah McKay

With just over six months until Britain leaves the European Union, May has yet to reach a deal with Brussels on the terms of the divorce, and her plan for future trade ties has been rebuffed by both the EU and many lawmakers in her own party.

Labour has listed six tests it would apply to any Brexit deal, including whether it ensured a strong future relationship with the EU and delivered the same benefits Britain has as a current member of the bloc’s single market and customs union.

“If Theresa May brings back a deal that fails our tests – and that looks increasingly likely - Labour will vote against it. No ‘ifs’, no ‘buts’,” Starmer will say in a speech to the party’s annual conference, according to advance extracts.

“And if the prime minister thinks we’ll wave through a vague deal asking us to jump blindfolded into the unknown she can think again... We will vote down a blind Brexit.”

Starmer will say the Conservative government does not have a credible plan for Brexit, and that there is no majority in parliament for May’s so-called ‘Chequers’ proposals, which envisage close ties with the EU in the trade of goods.

Labour could play a deciding role in whether any Brexit deal is approved by parliament. May has a working majority of just 13 in the 650-seat parliament and a former junior minister said this month as many as 80 of her own lawmakers are prepared to vote against a Brexit deal based on her Chequers proposals.

Labour published a document measuring the government’s progress against each of the tests which showed it was on course to fail all six. It said May needed to adopt a Brexit strategy that put the economy and jobs first.

Labour’s conference will vote later on Tuesday on keeping a second Brexit referendum as an option if May fails to get her Brexit plan through parliament, heaping pressure on a struggling prime minister.

“Labour seem determined to take us all back to square one by rejecting a deal out of hand then trying to delay Brexit and re-run the referendum,” junior Brexit minister Robin Walker said in a statement.

“Labour promised to respect the referendum result, but are just playing political games and trying to frustrate it.”