The commitment is an attempt to gain backing from opposition Labour Party lawmakers, who suspect the government plans to reduce the protections after Britain leaves the EU. May's deal has drawn opposition from both pro-EU and pro-Brexit lawmakers, and is facing likely defeat in Parliament on Tuesday.
The prime minister used a speech Monday to argue that the only alternatives to her deal were leaving the EU in March without an agreement, or reversing voters' decision to leave the bloc. May said that a no-deal Brexit would hurt the British economy and "put the future of our Union at risk," while failing to leave the EU would be "a subversion of the democratic process."
A top European Parliament leader is urging British lawmakers to "behave responsibly" and approve the UK's divorce deal with the European Union.
Manfred Weber said Monday that "we ask, we invite our British colleagues to behave responsibly and vote for this agreement."
A vote in the U.K. Parliament is expected Tuesday. Many British lawmakers object to the agreement between Brussels and Prime Minister Theresa May, raising fears that Britain may leave the EU on March 29 without a deal in place.
Weber, a German conservative who heads the biggest group in the European Parliament, said lawmakers in London should accept the "extended hand" of their colleagues on the continent.
He said the European Parliament will approve the agreement.
Weber also slammed the far-right Alternative for Germany party's threat to quit the EU, saying this could cause "a situation like in London today: economic instability and political chaos."
The British government has published a letter from European Union leaders that it hopes will ease U.K. lawmakers' worries over the Brexit agreement between Britain and the bloc.
The letter to Prime Minister Theresa May from European Council President Donald Tusk and European Commission President Jean-Claude Juncker offers an assurance that the most contentious part of the deal — the "backstop" insurance policy to maintain an open border between Northern Ireland and EU member Ireland — is intended as a temporary measure and "would only be in place for as long as strictly necessary."
But the letter also reiterates the bloc's refusal to renegotiate the divorce deal. The two men say "we are not in a position to agree to anything that changes or is inconsistent with the Withdrawal Agreement."
U.K. lawmakers are due to vote Tuesday on the Brexit deal, and it looks likely they will reject it.
British Prime Minister Theresa May plans to tell lawmakers she has received further assurances about her Brexit deal from the European Union, in a last-ditch attempt to win support for the unpopular agreement.
May is due to make a statement in the House of Commons Monday afternoon, a day before lawmakers are due to vote on her EU divorce deal.
May argues that defeating the deal could open the way for EU-backing legislators to block Brexit, with "catastrophic" results for Britons' faith in democracy.
A handful of previously opposed legislators got behind the agreement in the last few days, but they remain outnumbered by those determined to vote against it.
Defeat would throw Brexit plans into disarray, weeks before the U.K. is due to leave the bloc on March 29.