A THINK tank has questioned the independence of Scottish Parliament committees after backbench MSPs were made assistants to the ministers they are supposed to hold to account.

The respected Institute for Government warned that the system undermines basic principles of parliamentary democracy

Opposition parties have criticised the First Minister’s decision to offer a string of her backbenchers roles as parliamentary liaison officers (PLOs) to the ministers they are tasked with scrutinising in their committee sessions.

The think tank, which aims to improve government performance, said positioning a ministerial insider on committees could impede its effectiveness by deterring MSPs from speaking freely in private sessions because their comments may be reported back to the cabinet.

Ms Sturgeon made Kate Forbes, a member of the finance committee, PLO to finance secretary Derek Mackay, repeating the pattern across every cabinet brief. The move has been described as a Government power grab, as it ensures PLOs, who work closely with ministers and have access to confidential Government information, will supposedly also scrutinise their own boss.

Akash Paun, a fellow with Institute for Government, called on Holyrood to take heed of Westminster where the select committees have grown in stature and prominence.

“It’s a basic principle of parliamentary democracy that for Government to be effective, you have to have effective scrutiny of that Government and there has to be proper separation of powers between the executive and the parliament for that to happen," said he said.

"Certainly at Holyrood, it’s a unicameral parliament, the committees are a key part of scrutiny so it’s obviously very important that they are able to act independently of the executive and aren’t in some way influenced or controlled by ministers.

“The fact you have PLOs on the committees that are scrutinising the work of the minister those PLOs work for, I think it raises questions about the separation of powers between Government and parliament. I don’t think it automatically means those committees won’t be able to do their job properly, but it does raise questions about the extent to which those committees will be able to act fully independently, and have deliberations and decide upon conclusions and recommendations in reports in private without the minister knowing what’s going on.

“It sends an odd signal, to my mind, about what the role of committees is. It is, certainly, to be challenging to ministers, it’s not to make ministers’ lives easier.”

The SNP, which was once opposed to the practice of ministerial aides sitting on committees before reversing its position when they gained power, has previously dismissed criticism from opposition parties as "hysteria".

However, the intervention of the Institute will ramp up pressure on Ms Sturgeon to reintroduce a ban on aides sitting on committees tied to their minister’s brief.

It follows a string of concerns in the last Holyrood session over the performance of committees, which are tasked with quizzing ministers, scrutinising Government performance, launching enquiries, issuing reports and amending legislation. The Westminster equivalent of PLOs - parliamentary private secretaries - are not allowed to make any contributions in parliament linked to the minister or department they serve.

Mr Paun described the SNP as a “particular kind of party” that operates in “a very cohesive way” compared to Labour or the Tories at Westminster, where there is “a culture of independent backbenchers” who regularly defy their party line.

He added: “When the Scottish Parliament was set up there was all this emphasis on power sharing between Government and Parliament, having a strong committee system, and doing things better than Westminster. That vision, I think, it’s questionable that it’s been turned into reality. Scottish Parliamentary committees do some very good work, but I think Holyrood could learn some useful lessons from Westminster in this respect.”

A spokesperson for Joe FitzPatrick, the minister for parliamentary business, said the job of PLOs is to “provide a link between all parties, parliament as a whole and government ministers”. He added: “Committees in the Scottish Parliament have been operating independently for 17 years and will continue to do so.”