David Cameron is to attempt to persuade Conservative MPs to back a package of reforms he hopes will keep Britain in the European Union.
The PM will field questions in the Commons about the draft deal paving the way for the UK’s EU in-out referendum.
He said it would deliver the “substantial change” he has been demanding to how the EU is run.
But some Tories are sceptical, with one senior minister telling the BBC’s Laura Kuenssberg the deal was “a mess”.
MEPs will also debate the UK’s position when the European Parliament meets in Strasbourg.
The draft deal was published by European Council president Donald Tusk on Tuesday after months of negotiations between UK and EU officials, paving the way for the referendum to be held as early as June.
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It includes an “emergency brake” to restrict in work benefits for EU migrants. But it would have to be agreed by other EU nations and it would be “graduated”, with more money from tax credits paid to migrants the longer they remain in the UK.
The draft says Mr Cameron’s demand to exempt Britain from the EU principle of “ever closer union” between member states would be written into a future treaty, and there are also measures relating to protection for non-euro countries in the EU, a new way for member states to club together to block some new EU laws and on business regulations.
The prime minister will now embark on a whirlwind charm offensive to persuade the other 27 EU leaders to sign up to the package at a summit in Brussels on February 18-19.
Until a final deal is agreed with all the other member states, any Cabinet ministers who want to leave the EU have been told to back the government – but the BBC’s Laura Kuenssberg said there was debate behind closed doors over whether they should “stick to the previous deal and keep quiet until the middle of the month or gingerly begin to make the case for exit”.
Hailing the draft deal in a speech on Tuesday, the prime minister said “more work” needed to be done to “nail down” details but added: “We said we needed to deliver in four key areas, this document shows real progress on that front.”
He said the proposals were some “something worth fighting for”, and were good enough that he would back Britain joining the EU under these terms, if it was not already a member.
He said Britain could have the “best of both worlds” by giving it access to the single market and a voice around the top EU table, while retaining its status as a “proud independent country not part of a superstate”.
But the two main Out campaigns, Leave.Eu and Vote Leave, dismissed the package as meaningless, while UKIP leader Nigel Farage said it was “pathetic” and “hardly worth the wait”.
Labour leader Jeremy Corbyn, who will clash with Mr Cameron at PMQs before the EU statement, criticised the PM for failing to address MPs on the day the draft deal was published.