LONDON: Britain's former prime minister Theresa May said Monday she would not support the government's new Brexit legislation, which will break international law, accusing the government of acting "recklessly and irresponsibly".

May, whose 2016-2019 premiership was derailed by the tortuous Brexit process, said the draft law would "lead to untold damage to the United Kingdom's reputation".

"As a result, with regret, I have to tell the minister I cannot support this bill," she told fellow MPs as the proposed legislation underwent scrutiny in parliament.

The UK Internal Market Bill unveiled earlier this month would override parts of the Brexit treaty struck by May's successor Boris Johnson with the European Union last year.

Ministers have admitted it would breach international law.

British lawmakers voted last week to allow the draft law to proceed for further scrutiny despite EU calls for it to be withdrawn.

Numerous MPs from the ruling Conservatives cautioned against adopting the most contentious measures in the legislation, but only two ended up voting against it while 29 abstained -- including May.

Lawmakers will vote again on the bill on Tuesday next week before it goes to the House of Lords for weeks of further scrutiny.

Johnson has argued it will provide a "safety net" against what he has claimed are EU threats to impose tariffs on UK internal trade and even stop food going from mainland Britain to Northern Ireland.

But EU leaders have dismissed this as spin and warned Johnson to uphold commitments he made in the Brexit treaty last year and withdraw the offending parts of the new bill by the end of the month.

The row threatens to disrupt already tough post-Brexit trade negotiations, fuelling growing fears of failure that would see more than four decades of EU-UK integration come to a crashing halt at the end of this year.

Britain left the EU in January but remains bound by the rules of the 27-member bloc until December 31.