THE SNP have moved to block a second reading of the Tory government’s Withdrawal Agreement Bill (WAB) unless it is approved by the Scottish Parliament.

Boris Johnson’s administration is attempting to fast-track the legislation through the lower House in three days, potentially paving the way for the Lords to consider it over the weekend.

They will need MPs to approve a "programme motion" presenting the timetable for its passage through the Commons, setting up a crunch vote this evening.

But the SNP have submitted an amendment which would prevent the Bill having a second reading without approval from Holyrood.

The party’s Westminster leader Ian Blackford tweeted: "We have lodged an amendment to the withdrawal bill declining a second reading in the absence of the Scottish Parliament giving consent.

"Our right to determine whether we remain EU citizens must be in our hands not? @BorisJohnson."

READ MORE: Scottish judges reject bid to throw out Boris Johnson Brexit case

The Scottish Government has also recommended that Holyrood withholds consent for the WAB as it submitted a legislative consent memorandum.

Scottish Brexit Secretary Michael Russell announced the move on Twitter.

Many MPs are also deeply unhappy that there is so little time for detailed scrutiny of a such an important Bill, which runs to 110 pages with another 124 pages of explanatory notes.

Failure to get the motion through would open up the prospect that Johnson will be forced to accept another lengthy delay to Britain's departure – something he has vowed not to do.

The president of the European Council, Donald Tusk, has reassured MPs that a Brexit extension is still on the table.

READ MORE: Brexit: Donald Tusk hints at extension ahead of Commons showdown

The new Brexit deal must also win backing from the European Parliament but its Brexit co-ordinator, Guy Verhofstadt, suggested "all problems faced by EU27 nationals in the UK need to be solved" first.

His demands include no citizens being deported from Britain if they miss the deadline for settled status in order to prevent "another 'Windrush scandal".

The first Commons vote today will be on the Bill's "in principle" second reading.

Despite the opposition of the DUP over arrangements for Northern Ireland, ministers believe they have the support of pro-Leave Labour rebels and former Tory MPs now sitting as independents who would rather leave with Mr Johnson's deal than no deal at all.