Veteran SNP MP Pete Wishart has resigned from the party’s frontbench amid concern over changes in the Westminster leadership team.

Mr Wishart, who chairs the Scottish affairs committee and is the party’s environment spokesman, wrote to new leader Stephen Flynn accusing him of undermining his predecessor Ian Blackford.

His comments follow a vote on Tuesday by the 44-strong party bloc in the Commons to elect Mr Flynn as leader and Mairi Black as his deputy after Mr Blackford and his deputy Kirsten Oswald said they would not seek re-election.

Another frontbencher, Stewart McDonald, has said he will be stepping down as defence spokesman.

Mr Flynn has already replaced Owen Thompson as chief whip with Martin Docherty-Hughes being appointed to the role, and there are more changes expected to be announced in the coming days.

In his letter, Mr Wishart wrote: “I remain bemused as to the reasons why you felt it was necessary to seek a change in our leadership, particularly when we see yesterday’s opinion poll, which shows support for independence at a near all-time high and support for the SNP at Westminster at an unprecedented 51%

“Usually change of this significance accompanies failure, whereas we are looking only at sustained and growing success as a movement and party.”

He said that Flynn had been “canvassing opinion for a leadership challenge” and urged him to work closely with the party in Edinburgh.

Mr Flynn’s victory is seen as a challenge to the authority of Nicola Sturgeon who tried to stop the election and then failed to get her preferred candidate, Alison Thewliss elected to the post.

Mr Wishart, who represents Perth and Perthshire North, was first elected in 2001, making him the party’s longest-serving MP.

Stewart Hosie, the Dundee East MP, earlier this week claimed there was no truth in stories about divisions in the party, a view that will come under further scrutiny in light of Mr Wishart’s comments.