LONDON (Reuters) – The British government said on Thursday its key piece of Brexit legislation would be debated in parliament on Nov. 14 and 15, the next stage in what is expected to be a difficult lawmaking process that will test Prime Minister Theresa May’s authority.

The European Union (Withdrawal) Bill is central to the government’s Brexit plan, repealing the laws that made Britain an EU member and transposing existing EU law into British law.

But it has faced widespread criticism from members of parliament of all parties – including May’s Conservatives – for giving the government too much power to change laws, and for not guaranteeing parliament a vote on the terms of Brexit.

The much-anticipated first two days debate, of eight scheduled at the current legislative stage, were announced in parliament by Andrea Leadsom, leader of the lower house. The bill passed its first stage in September.

The bill had been expected earlier by some MPs, but the government said it needed time to look over the hundreds of proposed changes which will be discussed.

“Nearly 400 amendments have been tabled and we are looking at those with the utmost seriousness,” a Brexit department spokeswoman said.

“We look forward to continuing the debate and working with Parliament to ensure that we deliver a functioning statute book on exit day.”

Among the proposed changes, several have enough support from Conservative MPs to overturn May’s fragile working majority in parliament, which will test her ability to manage a party divided over the government’s Brexit plan.