The process to ensure the United Kingdom’s exit from the European Union progressed to the next stage on Tuesday after the House of Commons voted in favour of the EU Withdrawal Bill. The legislation framed by the Theresa May-led government was backed by 326 MPs in Parliament, while 290 voted against it, BBC reported.

May described the development as a “historic decision to back the will of the British people” and one that will provide “certainty and clarity”, The Guardian reported. Shadow Brexit Secretary Keir Starmer, however, described it as an “affront to parliamentary democracy”. Liberal Democrat Brexit spokesperson Tom Brake called it “a dark day for the mother of Parliaments”.

The prime minister’s Conservative colleagues have warned her that their support for the Bill was not unconditional and demanded several amendments to it. “Although there is more to do, this decision means we can move on with negotiations with solid foundations, and we continue to encourage MPs from all parts of the UK to work together in support of this vital piece of legislation,” May said.

The Bill changes provisions in the 1972 European Communities Act, under which the UK merged with the then European Economic Community. It will also change all existing EU laws into British law. The UK government will now have to make changes to the law to assuage fears that its ministers will be given sweeping powers.