The investigation into SNP finances has “moved beyond” the initial reports, Scotland’s most senior police officer has said.
Outgoing chief constable Sir Iain Livingstone also said the use of a police tent outside the home of former first minister Nicola Sturgeon had been necessary.
Mr Livinstone defended the police probe into the SNP’s finances – first launched two years ago – as “prudent and thorough”.
He said the investigation had moved beyond the initial complaints made to the force about how donations to fund a second independence referendum campaign were spent by the party.
Sir Iain told the BBC: “Investigations into the finances of an organisation, the finances of individuals, are often complex.
“Investigations around fraud or investigations around potential embezzlement or investigations around the misuse of funds take time.”
Judicial warrants are needed to obtain financial records, he added.
In recent months the probe has seen Ms Sturgeon arrested and questioned by officers for several hours before being released without charge.
Her husband – former SNP chief executive Peter Murrell – and party treasurer Colin Beattie were also arrested.
All have denied wrongdoing.
Sir Iain told the BBC’s Today programme he would have been accused of “dereliction and neglect of duty” if the force’s investigation had not been carried out in the way it had.
Top cop defends time taken to investigate SNP
“I know the full circumstances of the case,” he said.
“The tent was there, as were all the other measures, to protect the interests of justice and to protect the individuals involved.
“So it was a proportionate and necessary step.”
He added: “The time that’s been taken, in my judgment, is absolutely necessary.
“There’s been a prudent, thorough and proportionate investigation carried out.”
A dedicated team of specialists are involved, he said, and are working closely with prosecutors.
Speaking to journalists at an event in Fife on Wednesday, First Minister Humza Yousaf said his party will continue to co-operate with police.
Refusing to be drawn on the chief constables remarks, Mr Yousaf said: “I can’t (comment) because it’s a live police investigation.
“Obviously the comments Sir Iain Livingstone made are on behalf of Police Scotland and it is very much an operational matter for Police Scotland.
“All I can say is that the SNP will continue to do what we’ve done from day one and that’s fully co-operate with any police investigation.”