NATIONALIST MPs staged a sensational walkout during Prime Minister’s Questions today in a dramatic escalation of the post-Brexit devolution row — but opponents have accused them of “playing games.”

The SNP’s entire parliamentary party quit the chamber after its Westminster leader Ian Blackford was kicked out by the Speaker for disrupting proceedings.

Mr Blackford had been criticising the “democratic outrage” of the government pushing through EU withdrawal legislation without the consent of the Scottish Parliament, and with only 15 minutes to discuss the effects on devolved administrations.

The SNP MP called for the Commons to sit in private, a procedure by which to disrupt Parliament and demand a full debate, but Speaker John Bercow refused his call to take a vote on this there and then.

An ongoing brouhaha between the Westminster and Holyrood governments centres on whether powers taken back from Brussels after Brexit should immediately be devolved, or first go to Westminster.

This has led to the Scottish Parliament withholding consent from Brexit legislation. For the first time in history, Westminster has insisted on legislating in spite of this.

After today’s walkout, Mr Blackford said his party was protesting because the Tory government had “railroaded through amendments” over Brexit and devolution without parliamentary scrutiny.

“Not one single Scottish MP was able to speak in a debate that lasted less than 20 minutes,” he said. “That’s undemocratic, that is a slight to the Scottish Parliament and to the people of Scotland.”

Meanwhile Holyrood’s finance and constitution committee has called on Westminster Scottish Secretary David Mundell to give evidence “as a matter of urgency” to clarify London’s reasoning in pressing ahead.

Mr Blackford called for Mr Mundell to resign over the debacle in the Commons, and SNP MSP Ash Denham added: “The last 24 hours have made it perfectly clear — it’s time for David Mundell to go.”

After the walkout, Commons Speaker John Bercow said: “I really do think it would be a good thing if we perhaps brought to a close the operation of stunts and focus instead on the proper discharge of our responsibilities in this place.”

Mr Blackford said it was not a stunt and his party had a duty to “stand up for Scotland.”

But Scottish Labour deputy leader Lesley Laird said: “Today’s stunt by Ian Blackford and his colleagues simply emphasises further that they have one aim — to play political games rather than standing up for Scotland.

“They had a chance today to question the Prime Minister and secure a three-hour debate on devolution. Instead, they chose to flounce out of the House of Commons.”