Boris Johnson promised he would never agree to a Brexit deal like this under any circumstances

• Boris Johnson will on Saturday ask the UK Parliament to vote for his new Brexit deal with the EU.
• The deal is hugely controversial as it will lead to new customs checks on the Irish Sea between Northern Ireland and the rest of the United Kingdom.
• The prime minister had previously committed to opposing any new border checks on the Irish Sea.
• He said that "no British Conservative prime minister" could ever support a deal which included them.
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Boris Johnson will on Saturday urge members of United Kingdom's Parliament to back his new Brexit deal with the European Union.

Under the deal, the UK will cut all existing customs and trade ties with the European Union, with the exception of Northern Ireland, which will retain some trading arrangements in order to avoid a hard border with Ireland.

However, this decision means that there will need to be new customs and regulatory checks on the Irish Sea, effectively creating a new border between the two parts of the UK.

Read more: What is in Boris Johnson's new Brexit deal with the EU and what does it all mean?

Read more: The EU is preparing to delay Brexit if the UK Parliament rejects Boris Johnson's deal

This is hugely controversial, not least because Johnson has previously ruled out ever allowing such a division to happen.

In November 2018, he told the Democratic Unionist Party's conference that "no British Conservative government could or should sign up" to regulatory checks and customs controls on the Irish Sea, adding that to do so would risk "damaging the fabric of the Union."

He repeated this commitment in July 2019, during his campaign to become Conservative party leader and prime minister. 

Johnson told a meeting of Northern Irish Conservatives that "under no circumstances, whatever happens, will I allow the EU or anyone else to create any kind of division down the Irish Sea."

Read more: Boris Johnson's own official government figures shows his Brexit deal will make British people much poorer

Johnson's U-turn on this pledge has lost him the support of the DUP, which is now committed to opposing the deal when it comes to a vote on Saturday.