ALEX Salmond has given his colleague Angus Robertson his personal assurance that he will not seek to replace him as leader of the Westminster group of MPs after the General Election, The Herald has been told.

There is a growing expectation among media commentators in London and some voters that the former party leader and ex-First Minister will, if elected as MP for Gordon, automatically be crowned the Nationalist chief at Westminster given his status and profile.

Yet Mr Robertson, who is the party's election campaign chief and has held the Westminster leadership role since 2007 following Mr Salmond's election as First Minister, has told The Herald that he has been personally assured by his colleague that he will not seek to replace him as the party leader in the Commons.

Asked if he would continue to lead the SNP group at Westminster after May 7, Mr Robertson replied: "I'm delighted to serve as the Westminster leader of the Scottish National Party and will happily continue doing so."

The party rules state that it is the MPs, following an election, who determine who becomes their leader in the Commons.

The fact that the Nationalists are hoping to increase their number of MPs substantially after the election from six to, if the polls are right, anything from 30 to 50, could mean the choice of leader might not be so straightforward given Mr Salmond's high media profile not just north but also south of the border.

Asked about this, Mr Robertson replied: "It's amazing how many journalists at Westminster are behind on the news; journalists in Scotland and commentators in Scotland have been aware since Alex Salmond declared his candidacy in Gordon that he has confirmed he is not seeking the leadership of the SNP at Westminster."

But in, political terms, "not seeking" does not mean it will not happen. Politicians in the past have said they would not seek positions but, when colleagues have urged them to do so, have complied with their wishes.

When this was pointed out to Mr Robertson, he stressed: "I'm in the fortunate position of knowing Alex Salmond better than you do."

Asked if the ex-FM had given his personal assurance to his colleague that he would not seek the leadership, Mr Robertson replied: "Yes."

If the SNP does as well as the polls indicate it will, then the party will become the third force at Westminster, meaning, as a senior Commons source suggested, it would move from the "margins to the mainstream".

In such circumstances, the Nationalists would seek membership of most if not all Commons committees. Their leader would have his profile raised because during the weekly Prime Minister's Questions he would be called upon to ask two questions.

If, as Mr Robertson suggested, Mr Salmond did not become the SNP group's new leader, the 60-year-old politician could expect to take another key role, possibly as the party's Europe spokesman in the event of a Tory victory and an impending EU referendum.

At the weekend SNP conference, the party came under criticism when, in a behind-closed-doors session, it agreed to ban MPs from "publicly criticising a group decision, policy or another member of the group" in a move seen as strengthening the leadership's control. The proposal was said to have been passed "overwhelmingly" ie not unanimously.

Labour branded the move "Stalinist".