SNP leader Nicola Sturgeon has rejected reports of a “coup” against her Westminster chief as he announced plans to step down.

Ian Blackford announced on Thursday he would not seek re-election to the post at the SNP’s AGM next week, just weeks after reports Aberdeen South MP Stephen Flynn was manoeuvring to take over.

Mr Flynn stepped in to deny the rumours on Twitter, while Mr Blackford told the Scotsman just last week he would seek re-election and hoped to be “the MP which leads the SNP group out of Westminster for the last time”.

Speaking to STV News after First Minister’s Questions on Thursday, Nicola Sturgeon said: “No, it’s not a coup.

“Ian has been Westminster group leader for five years now and he represents one of the furthest flung constituencies in the country.

“He’s making the decision given all that lies ahead for the SNP, given all the exciting work that lies ahead for the SNP, that this is the right decision for him to pass on the baton.

“It’s up to the group now of course to consider who that is, but for now I want to pay tribute to the incredible, outstanding contribution that Ian Blackford has made.”

Mr Blackford denied he had been pushed out as leader, and when asked by Andrew Marr on LBC about conversations with colleagues encouraging him to go, told the broadcaster: “I haven’t had these conversations.”

The MP said it was his idea to step aside, and the “primary reason” was because Ms Sturgeon had asked him to be her business ambassador.

“That is something I’m so excited about, I’m delighted to take up that challenge. I can’t do that and play the role in Westminster as well,” he said.

Reports on Thursday afternoon suggested Mr Flynn has the required support to take over from the incumbent at next week’s vote.

Announcing his decision, Mr Blackford said: “I have today informed SNP MPs that I will not be re-standing as leader of the Westminster parliamentary group at our AGM next week.

“After more than five years in the role, now is the right time for fresh leadership at Westminster as we head towards a general election and the next steps in winning Scotland’s independence.”

Mr Blackford added that support for independence under his tenure has “continued to grow”, saying: “While I am stepping down as Westminster leader, I will continue in my role as the MP for Ross, Skye and Lochaber, and I have also accepted a new role at the centre of the SNP’s independence campaign, leading on business engagement.

“I would like to thank our MPs and staff for all their support over the past five years.

“Whoever replaces me as Westminster leader will have my full support as, together, we stand up for Scotland’s interests and democratic right to choose our future in an independence referendum.”

The last year of his leadership has been marred by his handling of allegations of sexual misconduct against one of his own MPs.

Patrick Grady was accused by a party staffer following an incident in a London pub in 2016.

He was later suspended from the Commons after an independent investigation and resigned his party membership, but the member of staff repeatedly criticised the SNP’s handling of the issue, saying his working environment had become “intolerable”.

Mr Blackford was also heard on a secret recording of a Westminster group meeting urging fellow SNP MPs to give Mr Grady their support.

SNP MP Joanna Cherry, who has regularly been at odds with the SNP’s leadership in recent years, welcomed the announcement of Mr Blackford’s departure.

She tweeted: “I’m pleased to hear this. It’s time for fresh leadership & tolerance of debate & diverse viewpoints.

“I hope @theSNP Westminster group will now be left to choose our new leader without outside interference & in accordance with our standing orders.”

Scottish Conservative chairman Craig Hoy claimed Mr Blackford had been “jumped before he was pushed”, adding the announcement was a “total humiliation for Nicola Sturgeon”.

He added: “She shamefully stood by her Westminster leader earlier this year despite his appalling handling of the complaints made against Patrick Grady.

“This showed a total lack of judgment by Nicola Sturgeon. Ian Blackford should have been sacked immediately for his disgraceful behaviour but he was allowed to stay in post for several months and now gets to dictate the terms on which he leaves.”

Shadow Scottish secretary Ian Murray said “the Nats are deserting the sinking ship”.

The Labour MP added: “Nationalist MPs know Nicola Sturgeon’s plan for a de facto referendum is finished before it’s even started and are worried about Labour gaining seats.”

Liberal Democrat MP Christine Jardine said her party is “breathing down (Ian Blackford’s) neck” in his Ross, Skye and Lochaber constituency.

Mr Blackford holds a majority of just under 10,000 votes in his seat.