PETER Mandelson has backed Tony Blair’s claim Brexit has strengthened the argument for Scottish independence.

But the former Labour Business Secretary warned that the SNP must consider the impact a break up of the UK could have on trade.

In a speech on Friday, the former prime minister said that Brexit made the prospect of independence “more credible”.

However, Lord Mandelson told the BBC’s Andrew Marr Show yesterday that independence would raise “a big question mark” over Scotland’s future trade with the rest of the UK.

The former European trade commissioner said: “Brexit strengthens the argument of the Nationalists, but that’s exactly what we warned during the referendum.

“But if you take the overall balance of the argument I don’t think it gives it to the Nationalists for this reason – over five, six times more amount of trade by Scotland is with the rest of the UK, not with the European Union.

“If they were to separate themselves from the UK, obviously, a big question mark would be placed over that trade.

“How would they do it if they separated from the UK, re-entered the European Union, the rest of the UK was out of the European Union, that would have an impact on Scottish trade with the rest of the UK and they have to take that into consideration.”

An SNP spokeswoman said: “Lord Mandelson is absolutely right that Brexit has strengthened the case for Scottish independence – not least because of the huge barriers to trade the Tories are erecting by dragging us out of the EU single market, which is around eight times bigger than the UK’s alone.

“But given the UK Government are promising a ‘seamless, frictionless’ border with the Republic of Ireland after Brexit, no amount of overblown claims from Lord Mandelson can give these claims about an independent Scotland any credibility.” Lord Mandelson also urged peers “not to throw in the towel early” over Brexit insisting the Government could still be defeated over key negotiating principles.

Protests will take place at Westminster today by workers from European Union nations who want the Government to guarantee their right to stay in this country post-Brexit.