LONDON (Reuters) – Brexit minister David Davis called on parliament on Thursday to back legislation to sever Britain’s political, financial and legal ties with the European Union, saying that opposing the bill would lead to chaos.

At a rowdy session of parliament, Davis accused the opposition Labour Party of pursuing a “cynical and unprincipled” path by challenging the repeal bill, or EU withdrawal bill, designed to disentangle Britain from more than 40 years of EU lawmaking.

Labour, in turn, said the government was using the bill to give itself wide-ranging powers and a “blank cheque” to do away with laws if ministers did not like them, threatening the rights of ordinary Britons.

The legislation is a vital stepping-stone towards Britain’s departure from the EU in March 2019. It faces stormy debate and a likely barrage of attempted amendments as Prime Minister Theresa May, weakened by the loss of her majority in a June election and criticized by Brussels over her Brexit strategy, attempts to steer it through parliament.

“Without this legislation a smooth and orderly exit is impossible … To delay or oppose the bill will be reckless in the extreme,” Davis told lawmakers, describing support for a proposed amendment by Labour as a “vote for a chaotic exit”.

Labour’s Brexit spokesman, Keir Starmer, said several clauses in the bill amounted to a “power grab” by government.

He said it would prevent Britain from remaining in the EU’s single market and customs union during a transition phase, as Labour now argues should happen.

“That we are leaving (the EU) is settled, how we leave is not. This bill invites us to surrender all power and influence over that question to the government and to ministers. That would betray everything we have been sent here to do,” Starmer said.

“Unless the government makes a very significant concession before we vote on Monday Labour will table, and has tabled, a reasoned amendment and will vote against the bill.”

“MASTERS OF OUR OWN LAWS”

The legislation seeks largely to ‘copy and paste’ EU law into British legislation to ensure the UK has functioning laws and the same regulatory framework as the bloc at the moment of leaving it, something that may offer some reassurance for companies.

Davis said it would allow the British government and parliament to become “masters of our own laws”, and promised concerned lawmakers that ministers would not use the wide-ranging powers to make “substantive changes” to law.

To vote down the bill, Labour would need to convince EU supporters in May’s Conservatives to side with them, but some more vocal pro-EU Conservative lawmakers have now said they will vote with the government after asking for reassurance that parliament will be able to scrutinize any changes to the law.

May has also promised to listen to the concerns of lawmakers, but warned that delaying or hindering the bill with amendments would slow “vital” legislation.

“The repeal bill helps deliver the outcome the British people voted for by ending the role of the EU in UK law, but it’s also the single most important step we can take to prevent a cliff-edge for people and businesses, because it provides legal certainty,” she said in a statement.