A major split has emerged between David Cameron and senior Conservatives in Scotland after the Tory leader refused to heed their calls to censure the Shadow Scottish Secretary for calling Tory MSPs “clueless” in a memo.

The divisions could come to a head today when the party’s crucial pre-election conference opens in Perth, with activists and MSPs joining forces to tell David Mundell not to turn up and saying that they can no longer work with him.

One senior Conservative at Holyrood told The Times: “We just do not think there can be any relationship between David Mundell and the Tory group at Holyrood after this. He is certain to be booed by everyone in Perth. He’ll be lucky not to get slapped.”

The row added to a deeply uncomfortable day for Mr Cameron who had to sack a member of his front bench, Patrick Mercer, over racist comments.

The memo, which was sent to Mr Cameron and leaked to a tabloid newspaper, has the party in turmoil. Several senior party figures are understood to have called Mr Cameron’s office and told him to take action against Mr Mundell.

“We have made our views abundantly clear,” one said.

While Mr Cameron publicly backed Annabel Goldie, the Scottish leader, and Peter Duncan, the Scottish chairman — both subjected to scathing criticism in the memo — he stopped short of sacking Mr Mundell. But a statement released by Mr Cameron noticeably failed to extend any praise to his Mr Mundell, who spent most of yesterday keeping a low profile in his constituency.

Mr Cameron’s unwillingness to act may have had much to do with the fact that Mr Mundell is the only Scottish Tory in the Commons. If he sacked Mr Mundell, he would have had to replace him with an English MP.

Mr Cameron cannot plead ignorance of the memo or its contents since it was written for his attention last June. The memo amounts to a scathing assessment of the state of the party in Scotland.

In it, Mr Mundell, himself a former MSP who switched to Westminster in 2005, said that there was a “simple lack of thinkers” on the Conservative benches at Holyrood who were incapable of formulating their own policy independently.

He said that Ms Goldie had made a reasonable start but was guilty of “lack of activity and strategic thought”. She had “sensitivities” about how she was presented alongside Mr Cameron, who has referred to her in the past as his “Scottish auntie”. The need to replace Mr Duncan was, Mr Mundell said, an “immediate priority”.

He said: “There are more problems than solutions emanating from Scotland from a party point of view. I see little in the short term that can be done to improve the MSP group situation.”

Mr Cameron said in his statement: “Annabel Goldie and Peter Duncan are doing a great job. Annabel has a no-non-sense approach and is addressing the issues that really matter in Scotland.

“The party in Scotland is in better health now than it has been for many years and is running an effective campaign. I am looking forward to the Scottish conference.”

Asked why Mr Mundell had kept his job, Mr Cameron’s spokesman, said: “David Cameron decides who is in the Shadow Cabinet. There is no reason to suggest there are going to be any changes on that front.”

Lord Foulkes, the Labour Party campaign chairman, said the memo showed that Conservative MSPs were simply not up to the job.

“I would join the growing list of people calling for Mr Mundell’s head were it not for the service he has done for the people of Scotland, revealing as he has the sheer mediocrity of the Tories in the Scottish Parliament,” he said.

Angus Robertson, the SNP campaign director, said: “Nothing that the SNP or anyone else might say about the Tories in Scotland could be as devastating as this candid assessment by their own shadow Scottish secretary.”

Iain Smith, a Liberal Democrat MSP, said: “I find myself in the peculiar position of agreeing with a Conservative politician.”

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