THE Scottish and UK governments are on a new constitutional collision course after SNP ministers recommended Holyrood should reject the law that would ‘get Brexit done’.

SNP Brexit Secretary Michael Russell told his UK counterpart he was urging MSPs to withhold legislative consent from the EU Withdrawal Agreement Bill (WAB).

It means Westminster will almost certainly have to impose the legislation on Scotland without Holyrood’s agreement, despite it covering a number of devolved areas.

This has happened only once before since 1999 - when Westminster imposed the original Brexit withdrawal law on Scotland last year, in spite of MSPs voting 93 to 30 against it.

MPs this afternoon voted in favour of the general principle of the WAB by 358 to 234, with more detailed debate due when the Commons returns in January.

Another confrontation is likely to raise questions about the value of the Sewel convention, which says Westminster will not “normally” legislate in devolved areas without Holyrood’s express consent.

The WAB and a slew of other Brexit-related Bills are likely to see the convention breached time and again in the coming months.

The Sewel convention is only a political practice, and carries no force in law.

Mr Russell also published a legislative consent memorandum setting out the Scottish Government’s reasoning.

This is an updated and expanded version of the memorandum he issued in October, when the WAB was published in its original form before the election.

The new memorandum covers the election result and a series of changes and dilutions made to the WAB now that Boris Johnson has a safe Commons majority.

One notable change is that the revised document, in contrast to Nicola Sturgeon’s claim she has an Unarguable mandate” for a second independence referendum, says there is “no democratic mandate” for Brexit in Scotland.

It says: “Therefore the Scottish Government cannot support a Bill that implements the exit of Scotland, as part of the UK, from the EU.

“It cannot recommend that the Scottish Parliament consent to a Bill to give effect to an agreement which it considers will do significant damage to Scotland.”

Although the Scottish Government's move had been expected, it adds to the intensifying fight between Edinburgh and London over a second independence referendum.

On Tuesday, Nicola Sturgeon said that if Westminster passed the WAB without Holyrood’s consent it would show “contempt for devolution” and a willingness to tear up constitutional rules in pursuit of Brexit.

If the WAB is indeed imposed, the First Minister will cite it as further evidence of Scotland being disrespected and maltreated within the Union.

In his letter to Brexit Secretary Steve Barclay, Mr Russell said: “The people of Scotland have voted clearly and decisively against leaving the EU on each and every opportunity they have had, from the referendum in 2016 to the UK General Election on 12 December.

“The Scottish Government cannot therefore recommend to the Scottish Parliament that it consents to the Withdrawal Agreement Bill. We have today lodged with the Scottish Parliament a legislative consent memorandum setting out our reasons for this position.”

Mr Russell said it was “unfathomable” that the UK Government wanted to use the WAB to prohibit an extension of the transition period beyond December 2020, crearting a lack of flexibility in trade talks with the EU that could lead to a no-deal Brexit on WTO terms.

He said: “This proposal dramatically raises the risk of a no deal exit at the end of 2020, or agreement of only an extremely limited future partnership. If there has been any lesson from the last three years, it is we should take time to achieve the right kind of future partnership.

“The UK Government should work to build consensus, with the full involvement of the devolved administrations, rather than rush to impose its own narrow views on everyone else.

“I note your comments on collaboration between officials on the drafting of the Bill, and I am happy to repeat my acknowledgement of these.”

A UK Government spokesperson said: "The Prime Minister has delivered a great new deal that works for all parts of the UK. 

"It is disappointing that the Scottish Government has so far refused to recommend legislative consent and are instead using this process to signal their opposition to Brexit.

"Throughout the Brexit process, we have regularly engaged with the Devolved Administrations and we will continue to do so."