BORIS Johnson was warned his government’s willingness to break international law could lead to a “wildcat” referendum on Scottish independence.

On Tuesday, the Northern Ireland Secretary Brandon Lewis shocked MPs when he admitted that the UK Government is set to break international law in a bid to override the Brexit deal in a “very specific and limited way”.

At Prime Minister’s Questions, LibDem MP Alistair Carmichael asked on what ground the Tory Government could now oppose an indyref held without a Section 30 order. He said: “There are some Scottish nationalists who want Scotland to follow the example of Catalonia and to have a wildcat independence referendum. Now, I oppose that, because it would be illegal. If the Prime Minister thinks it’s acceptable for his Government to ignore international law, on what basis would he oppose it?”

Johnson instead explained why his Government is seeking to change the Northern Ireland protocol agreed with the EU earlier this year.

He said: “My job is to uphold the integrity of the UK but also to protect the Northern Irish peace process and the Good Friday Agreement and to do that, we need a legal safety net to protect our country against extreme or irrational interpretations of the protocol which could lead to a border down the Irish Sea in a way that I believe would be prejudicial to the interests of the Good Friday Agreement and prejudicial to the interests of peace in our country, and that has to be our priority”.

The question over the legality of an indyref without a Section 30 order is much debated by independence supporters.

It effectively gives the UK Government the legal power to alter the list of reserved matters which fall outside Holyrood’s powers.

Nicola Sturgeon has made clear she wants ministers in London to agree to allow Holyrood to “enable a referendum to be put beyond legal challenge”.