The Scottish Parliament has "no role" in passing the Brexit deal into law, the Prime Minister has said.

Boris Johnson was responding to SNP Westminster leader Ian Blackford's call to respect the convention that UK legislation which affects Scotland should have Holyrood's consent.

Speaking at Prime Minister's Questions on Wednesday, Johnson told MPs "it is up to the members of this parliament" to approve the deal - not MSPs.

However, explanatory notes to the PM's withdrawal agreement bill (WAB) set out more than dozen areas where the UK Government is expected, under longstanding political convention, to formally seek Holyrood's consent.

It comes as First Minister Nicola Sturgeon and Welsh First Minister Mark Drakeford held a joint press conference in Westminster to condemn the WAB

For the first time in the history of devolution, the Scottish and Welsh parliaments could both refuse to consent to the legislation.

Johnson announced a "pause" on the WAB's passage on Tuesday after MPs rejected his bid to hurry it through the Commons this week, although they backed the deal in principle.

The UK Government is waiting to learn on what terms the EU will offer a Brexit extension before it decides how to proceed.

The Prime Minister has said a lengthy delay would see him push again for snap general election.

Speaking in the Commons, Blackford said: "Within the last hour, the first ministers of Scotland and Wales joined forces to oppose this Tory government's damaging Brexit Bill, a bill that risks jobs, opportunities and our entire economic future."

He asked: "Will the Prime Minister stop ignoring Scotland and confirm today that he will not allow this legislation to pass unless consent is given by the Scottish Parliament - yes or no Prime Minister?"

Johnson replied: "I note very carefully what the honourable gentleman had to say, but he knows that the Scottish Parliament has no role in approving this deal.

"On the contrary it is up to the members of this parliament to approve the deal."

In response, Blackford said: "Well, there we have it: the legislative consent that the Scottish Parliament is asked for is meaningless in the Prime Minister's eyes.

"So much for the respect agenda, so much for the message in 2014 that we were to lead the United Kingdom, that this was a union of equals - torn asunder by the disrespect of this Prime Minister."

He continued: "He must now secure a meaningful extension and bring on a general election - let the Scottish people decide our future in Scotland."

The Prime Minister said Blackford's call for an election was an "exciting development" and suggested that he "pass... some of that courage down the line" to Labour leader Jeremy Corbyn.

The Scottish Parliament can formally refuse to approve UK legislation which affects Scotland through a legislative consent memorandum (LCM).

Under the Sewel Convention, the House of Commons is not expected to legislate in devolved areas without Holyrood's express agreement.

The WAB's explanatory notes identify 17 areas of the bill - including on citizens' rights and welfare - which would require the approval of MSPs under Sewel.

However, in practice the UK Parliament would not be prevented from passing legislation, as the convention gives devolved administrations no legal powers to veto laws at Westminster.

Last year, MSPs refused consent to the so-called "repeal bill" dealing with powers coming back from the EU, but the Commons was still able to pass it.