STEWART Hosie has dramatically announced his decision to quit as the Nationalists’ deputy leader in the wake of the so-called “SNP love triangle”, saying he has found the stress caused by the intense scrutiny of his private life very difficult.

In a resignation letter to Nicola Sturgeon, the Dundee East MP apologised for “any hurt and upset” he had unintentionally caused his friends, family and colleagues after his affair with a journalist was exposed and which led to the separation from his wife, Shona Robison, the Scottish Health Secretary and one of the First Minister’s closest friends.

Mr Hosie, 53, is alleged to have had an affair with Serena Cowdy, 36, a former actress, who was previously said to have been involved with his SNP colleague Angus MacNeil, who represents Na h-Eileanan an Iar and chairs the Commons energy committee.

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Today, Ms Sturgeon will arrive at Westminster to address her party’s MPs following the SNP’s victory in the Holyrood elections. A Commons photocall is due to take place but the event is likely to be overshadowed by the controversy and Mr Hosie’s decision to quit as the party’s leader deputy.

It had been expected that he would head up the SNP’s new summer campaign for Scottish independence. But a party source said that it was never officially confirmed that Mr Hosie would lead it but that, given what had happened, his involvement would now be “much less than previously anticipated”.

The Herald:

His Westminster colleague, Pete Wishart, the SNP’s shadow Commons leader, tweeted on hearing of Mr Hosie’s decision to quit: “Really sad but totally understand why Stewart Hosie would want to stand down...He’s been a fantastic deputy in the party.”

Labour’s Ian Murray, the shadow Scottish secretary, said Mr Hosie had made the right decision to resign but that the incident exposed “something more significant about the SNP at Westminster”.

He said: “Last year, the SNP told us their MPs would be stronger for Scotland but just 12 months on many have been a source of real embarrassment.

Read more: Stewart Hosie resignation - Exchange of letters between Nicola Sturgeon and outgoing deputy leader

"This incident hasn't just seen them let down their party but they are letting down the people of Scotland, who voted for them and expect much better behaviour," added the Edinburgh MP.

In his letter to Ms Sturgeon, Mr Hosie explained that he was informing her now that he would not be seeking re-election as deputy leader at the SNP’s autumn conference in order to give “ample time for the party to choose a successor”.

He pointed out that he had been admitted to hospital on three occasions in the past few years with very high blood pressure. “In that regard, the stress of the intense scrutiny of my private life has been very difficult. I intend to concentrate on my constituents, my responsibilities at Westminster, and most importantly, my health.”

The Herald:

He added that it had been a “pleasure to serve under your leadership and I hope to do so for many years to come. I wish you, your Government and our party every success”.

In a letter of response, Ms Sturgeon thanked Mr Hosie for his service as the party’s deputy since November 2014, noting how he had written two successful election manifestos, “achievements you should be very proud of”.

Stewart Hosie to step down as SNP's deputy leader in wake of controversy over private life

She added: “I have enjoyed working with you as depute leader and I look forward to continuing to work with you in the future. I wish you well.”