The government is facing a second heavy defeat on its Brexit deal after the Attorney General poured cold water on the Prime Minister's "legally binding" changes to the withdrawal agreement.

MPs are set to get their second meaningful vote on the Brexit deal tonight, just 17 days before the UK is set to leave the European Union.

In a statement released to the Commons, the government's top lawyer Geoffrey Cox MP said that the PM had secured: "legally-binding changes that strengthen and improve the withdrawal agreement and political declaration."

However, the crucial factor for some MPs is over what happens if a future agreement cannot be agreed with the EU - when the Northern Ireland Backstop would be engaged.

The Attorney General said such an outcome would be "unlikely to occur" and that the decision MPs face when they vote on Tuesday evening was a "political judgement."

He added: "Were such a situation to occur, the legal risk as I set it out in my letter in November... remains unchanged."

The previous vote saw the government lose 432 to 202 with many calling for a significant change to be made to the Northern Ireland Backstop agreement.

Last night, Prime Minister Theresa May said she had secured "legally binding" changes to the withdrawal agreement between the UK and EU.

In a joint press conference with the president of the EU commission, Jean-Claude Juncker, May said that she "passionately believed" that the additional agreements would alleviate any concerns over the Backstop.

Many MPs fear that the Backstop could lead to the UK being effectively left in a customs union with the EU indefinitely if no agreement is finalised with Europe.

The vote is due to take place at 7pm this evening.

If it fails, a second vote will take place tomorrow on whether the government should take the possibility of a 'no deal Brexit' off the table.

Depending on the result of that vote, a third would then be scheduled for Thursday over whether to extend the Article 50 period beyond March 29, effectively delaying Brexit.