An SNP MP has said a proposed route to independence which would avoid a Westminster veto should be 'put to bed' - amid fears it could force Scotland into a 'hellish limbo' like Catalonia.

Pete Wishart said the so-called 'Plan B' route to Scottish independence would in effect mean declaring 'some sort of Unilateral Declaration of Independence'.

The Perth and North Perthshire MP called for clarity on the proposal, and says that the time for such a route 'has not come yet'.

"My little bit of advice to my good friends in the ‘Plan B movement’ is to at least come up with some sort of concrete proposal so we can have some idea what it is we are supposed to debate," he wrote on his blog.

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"‘Just doing it anyway’ means we would be doing something broadly similar to what Catalonia did when they ‘won’ their uncontested referendum – without actually winning a referendum! This would in effect mean we would be declaring some sort of Unilateral Declaration of Independence (UDI).

"The consequences of that could not be more serious. Almost certain to be one of the first things to happen is that we would have all of this immediately ruled illegal and be disenfranchised from the entire international community. We would be left in the sort of hellish limbo currently endured by the people of Catalonia."

The 'Plan B' route would see Scotland avoid a Westminster veto to achieve independence.

SNP MPs attempted to have a debate on the idea at the party's conference, which would have allowed members to discuss whether or no a pro-independence majority at an election could be a mandate to open negotiations with the UK.

The unsuccessful attempt would have put pressure on the Prime Minister to grant a Section 30 order.

Wishart also argued that the SNP have a good chance of securing a majority at next year's Holyrood elections - which would allow for negotiations on 'Plan B' to begin.

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He said: "That would therefore mean that the 2021 election ceases to be a General Election in the conventional sense and instead becomes a single issue plebiscite exclusively on the proposition that if the SNP secures a majority we move towards becoming an independent state.

"If it was to happen there would be no programme for Government, no defence of a record in power, just a straight forward one issue independence question."