THE SNP are being urged to make clear it will continue to co-operate with the police inquiry into its finances when its new chief executive takes up his role this week. 

Murray Foote, who takes up the post tomorrow, launched a ferocious attack on Operation Branchform in May, calling the search by officers of Nicola Sturgeon's and Peter Murrell's house a "grotesque circus".

He also accused officers of “storming” the SNP headquarters and wrote that the probe could turn into a debacle with "serious consequences" for the authorities like the failed Rangers prosecutions which cost taxpayers £50million. 

READ MORE: Who is Murray Foote, the SNP's new chief executive?

In the same article the former spin doctor also said that it was "worth" considering whether Operation Branchform is a "wild goose chase" and used the derogatory description of "plod" when referring to officers searching the couple's home in April.

The Scottish Liberal Democrat MSP Willie Rennie called on Mr Foote to write to Police Scotland and the Crown Office, which is also working on the inquiry, to "assure" both organisations of the SNP's continued operation.

"Murray Foote is the highest profile SNP figure to have poured scorn on the police investigation," said Mr Rennie.

"I suspect the police will not be thanking Humza Yousaf for appointing such a prominent critic of their work to head the SNP.

READ MORE: Murray Foote, who called SNP police probe 'grotesque', is party boss

"Given that Murray Foote is now in a position where he may be called upon to help the police with their inquiries, it would send a positive message if he would write to Police Scotland and the Crown Office to assure them that the SNP will continue to co-operate with the ongoing investigation."

Scottish Conservative chairman Craig Hoy also raised concerns. 

“Humza Yousaf’s decision to give the top job in the SNP to someone so closely linked with the discredited Murrell-Sturgeon axis is preventing his party from learning, or moving on, from the scandal that engulfs it," he said.

“The SNP should be fully co-operating with the police, who are duty-bound to investigate a very serious matter, yet, in Murray Foote, they have appointed a chief executive who has been openly critical of Operation Branchform. 

The Herald:

Sir Iain Livingstone, the former chief constable of Police Scotland, defended the investigation after it came under attack.

“This is deeply concerning, and it’s precisely why Humza Yousaf ought to have appointed someone unconnected with the SNP’s recent past.”

Mr Foote, the former editor of the Labour-supporting Daily Record, was the architect of The Vow on the eve of the 2014 referendum.

READ MORE: Operation Branchform: Police chief rejects attacks on SNP probe

He quit as the SNP’s Holyrood communications chief in March after being misled by colleagues at HQ about the party losing a third of its members.

After unwittingly misleading the media in turn, Mr Foote resigned saying the episode had created “a serious impediment to my role”.

His exit piled huge pressure on then chief executive Mr Murrell, who resigned the next day after two decades in charge.

Mr Murrell was arrested and questioned by the police in April as part of Operation Branchform, the two-year probe into SNP fundraising.

Former SNP national treasurer Colin Beattie and Nicola Sturgeon were also arrested and questioned as part of the investigation in April and June respectively. All three senior SNP figures were released without charge.

READ MORE: Operation Branchform: SNP probe handed to deputy after chief retires

The initial raid on the Murrell-Sturgeon home in Glasgow on April 5 saw police erect a blue evidence tent on the couple’s front lawn.

Officers also raided SNP HQ in Edinburgh and seized a £110,000 luxury motorhome from outside the Fife home of Mr Murrell’s 92-year-old mother.

In May, Mr Foote wrote an article in the Daily Record where he was scathing about the probe.

He said: “The use of forensic tents and a whole platoon of plod at the house turned a routine process into a grotesque circus, compounded by the storming of SNP HQ. 

"It is inconceivable to me that Peter would so much as consider doing something dodgy lest it rebound and put his wife in jeopardy.

"Colin is no-one’s fool. He is a capable, cautious and diligent MSP who values his integrity.

"So I’m prepared to gamble the Foote £5 on no charges at the end of all this. Should that bet be a winner, then the police and Crown Office will find themselves together in a very deep hole.

"Police diligently going about their business is one thing. What happened at the FM’s home is something else entirely.”  

The former chief constable of Police Scotland, Sir Iain Livingstone, who retired last week, repeatedly defended his force's investigation from criticisms made by Mr Foote and others.

Speaking last month Sir Iain said: “There's been a prudent, thorough and proportionate investigation carried out. I have been aware of this investigation since the outset. 

“It has got a dedicated team of specialists who are involved in it and they are working very closely with our prosecutors, the Crown Office in Scotland, in terms of the steps that are taken. 

“What I would say is that had we not carried out this investigation in the manner we have, I would rightly have been accused of a significant dereliction and neglect of duty. 

“That's not the case. We've done the right thing. The rule of law and the interests of justice must prevail.”

The SNP have previously said they will co-operate with the inquiry.

After her release, Ms Sturgeon told journalists: "I am absolutely certain that I have done nothing wrong."

The SNP were approached for a response to Mr Rennie's and Mr Hoy's comments.

After the party declined to comment, Mr Hoy added: "Who do the SNP think they are kidding?

“It is perfectly legitimate to question them appointing to the top job someone who has been so disparaging about a major police investigation into the party’s finances.

“For ‘not dignifying with a response’ read: ‘we can’t think of a defence’.”