London - Leading eurosceptic lawmakers in British Prime Minister Theresa May's Conservatives look set to oppose her revised Brexit deal late Tuesday, making another parliamentary defeat likely.

Lawmakers to vote on the deal

Conservative lawmaker Bill Cash said he and other legal advisers examined the advice given to May by Attorney General Geoffrey Cox and concluded that it "does not meet the tests the government set itself," despite May's claim to have secured legally binding improvements in last-minute talks with EU leaders.

"In the light of our own legal analysis and others we do not recommend accepting the government’s motion today," Cash said on behalf of the European Research Group (ERG) of some 80 Conservative eurosceptic lawmakers.

Lawmakers will vote on the deal after May said she had secured legal assurances in last-minute discussions with EU leaders late Monday.

In a blow to May, Cox said the risk of Britain remaining in an indefinite arrangement with the European Union to protect an open Irish border after Brexit remained "unchanged."

He said there was still a legal risk of failed trade talks leaving Britain trapped in the so-called "backstop" arrangement, which is designed as a temporary, last-resort measure to guarantee and open Irish border.

Cox said the EU's assurances did reduce the risk that Britain could be "indefinitely and involuntarily detained" in the backstop - designed to keep an open border between Ireland and Northern Ireland after Brexit - because of "bad faith" in negotiations by the EU.

Speaking in parliament later, he urged lawmakers to back May's deal, saying their decision was ultimately "political" rather than legal.

In a statement from the group's legal advisers, published on Twitter by deputy chair Steve Baker, the ERG said the withdrawal agrement still does no provide "any exit mechanism form the [backstop] protocol which is under the UK's control."

It said Cox's claim that "bad faith" by the EU could provide away out of the protocol "is not credible in practice."

May suffered a defeat in the first vote

The eurosceptics are concerned the backstop - intended as a temporary, last-resort measure - treats Northern Ireland differently from the rest of the United Kingdom and could become a permanent arrangement if post-Brexit trade talks fail.

With Britain set to leave the EU on March 29, barring any delay to that plan, time is running out for lawmakers to agree on the way forward.

May suffered a crushing defeat in the first vote on her Brexit deal in mid-January.

Labour, the main opposition party, said her last-minute negotiations had failed and had not changed the deal on the table.

Cox's advice confirms that there have been "no significant changes" to the withdrawal agreement, leaving the government's strategy "in tatters," said Keir Starmer, Labour's Brexit spokesman.

Labour leader Jeremy Corbyn said earlier that the agreement in Strasbourg "does not contain anything approaching the changes Theresa May promised parliament."

If May loses Tuesday's vote, parliament is expected to hold two more votes on Wednesday and Thursday on whether Britain should leave the EU without a deal, and if it should extend the Brexit negotiations.