Scottish Labour MSPs have raised “serious concerns” over the apparent shift in national party policy on a second independence referendum.

The intervention follows John McDonnell’s comments at the Edinburgh Festival this week, which saw the Shadow Chancellor claim that Labour would not block another public vote if a majority of MSPs voted in favour of one.

The remarks defied the previously stated view of Richard Leonard, Labour’s Scottish leader, who has said that a Labour government would refuse to grant the order under Section 30 of the Scotland Act 1998 allowing a fresh independence referendum to be held.

The Scottish Parliamentary Labour Party (SPLP) have released a joint statement this afternoon expressing disapproval of McDonnell’s comments. It reads: “We deplore any attempts to undermine the official policy position of the Scottish Labour Party and we express serious concerns about an apparent change in Labour’s position on a matter of vital importance to the future of Scotland and of the Scottish Labour Party itself.”

The statement, which does not include a list of signatories, was organised by the Scottish parliamentary party chair Jackie Baillie and approved by a majority of SPLP members. LabourList understands that that although it explicitly conveys “support” for “the stance taken by Richard Leonard as our leader”, it was not sanctioned by the Scottish Labour leader’s office.

“It is not really a supportive statement,” a Scottish Corbynite source told LabourList. “It was put out by elements of the right in Scotland who want rid of Leonard.”

Commenting on the row over Labour’s stance on Wednesday afternoon, Leonard said: “I met with John this morning, and I made clear to him that a second independence referendum is unwanted by the people of Scotland and it is unnecessary. The 2014 referendum was a once in a generation vote.”

Below is the full text of the SPLP statement.

The Scottish Parliamentary Labour Party has already opposed a divisive and unnecessary second independence referendum and will campaign tirelessly to ensure Scotland remains part of the United Kingdom. The people of Scotland were told that the 2014 independence referendum was a once-in-a-generation contest.

The SPLP support the stance taken by Richard Leonard as our leader and back the policy position that he outlined. We deplore any attempts to undermine the official policy position of the Scottish Labour Party and we express serious concerns about an apparent change in Labour’s position on a matter of vital importance to the future of Scotland and of the Scottish Labour Party itself.

Scottish Party policy is very clear – that is opposition to a second independence referendum. There is therefore an urgent need for the UK party leadership to engage constructively with the Scottish Party leadership on the issue of the party’s stance on the future of Scotland.

We are clear Labour’s position on Scotland’s future is a decision for Scottish Labour, which the UK Party must accept. We expect all Scottish Labour MPs and MSPs to vote in accordance with party policy.