SENIOR SNP MP Pete Wishart is facing “disciplinary action” after defying the party leadership for a second time in a Commons vote.

But the Perth and North Perthshire MP admitted he was "not overly concerned” about any sanction he might face given he wrote the disciplinary rules when he was the party’s Chief Whip at Westminster for 10 years.

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Last week, Mr Wishart took the unusual step for a Nationalist MP of rebelling after the party managers whipped MPs to support a Brexit alternative option of having a confirmatory referendum on any deal.

During the second round of indicative votes on Monday night, the backbencher again failed to vote with his colleagues but instead once more abstained.

Last week, his Nationalist colleague Angus Brendan MacNeil, who represents Na h-Eileanan an Iar, also abstained but was unable to take part in Monday night’s vote because he could not get a flight down to London because of military air space restrictions.

The two MPs believe strongly that having a confirmatory referendum on a previous vote could have serious implications if there were a second poll on Scottish independence.

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Mr Wishart has explained that he “could not in full conscience” support the proposal for a confirmatory vote as it would be an “open invitation” to the UK Government to strike the worst possible exit deal with Scotland, should voters opt for independence, to stoke resentment and reverse the result.

The MP, who entered Parliament in 2001, said his decision to rebel was a “tough one” but taken in what he believed was in the best interests of his constituents and of the nation.

Given there could be another vote that included a confirmatory poll, Mr Wishart was asked if he would rebel a third time. He said that he would consider the options at the time, stressing he had not ruled out supporting a confirmatory vote. “If it was the only way forward to stop Brexit, given all my concerns, I would vote for it. I’m not ruling anything out.”

A party source confirmed the MP was facing a disciplinary process led by the current Chief Whip Patrick Grady. But Mr Wishart told The Herald: “I’m not overly concerned about that. I designed the process when I was Chief Whip.”

It appears any sanction would simply involve his local party being told of his transgression and it would take it into consideration when deciding who it wanted its election candidate to be.

Meanwhile, 25 Labour MPs defied Jeremy Corbyn by voting against the Norway-style option and 24 voted against the confirmatory vote option.

Among the rebels was Ian Lavery, the party Chairman, who abstained on the whipped confirmatory vote option, promoted by his Labour colleague Peter Kyle.

There were calls for the Northumberland MP to resign from his party post. Edinburgh MP and a leading Remainer Ian Murray noted: "You either serve in the Shadow Cabinet or you break the whip. You can’t do both. It’s a choice you have to make.”

Mr Lavery defended his decision by saying: "We had a referendum and 17.4m people voted to leave the European Union and we’ve got to respect what they have to say."

A party spokesman said the indicative votes process was “exceptional” but any disciplinary action was a “matter for the leader and the whips".

The Conservatives had a free vote on all four motions.

Some 36 voted for the customs union proposal, tabled by former Chancellor Ken Clarke. They included Scots Luke Graham and Paul Masterton.

A total of 32 backed the Norway-style option, that called for single market membership and a customs arrangement. They included Mr Masterton and his Scottish colleagues Stephen Kerr and Bill Grant.

Some 14 Tories backed the confirmatory vote option and nine the so-called parliamentary supremacy option that could lead to scrapping Brexit altogether to avoid a no-deal outcome.