THE next Information Commissioner needs extra powers, including the ability to demand evidence under oath, to prevent public bodies right up to the Scottish Government backsliding on their obligations.

That is the view of the outgoing commissioner, Kevin Dunion, who leaves office next month concerned that Scotland's lead in freedom of information (FoI) is being steadily eroded by advances south of the Border and resistance at the top by some Scottish ministers.

Dunion leaves office next month and today he will be questioned by MSPs at the Justice Committee on a hard-hitting final report that makes a series of recommendations.

He repeats his strong belief that private bodies carrying out public work must be designated under FoI; that there must be no hike in charges; that the timescale for prosecuting those who destroy evidence must be extended; and that the commissioner should be given the power to take evidence under oath.

Mr Dunion is arguing for the adoption of the Canadian system, where his counterpart is empowered to take sworn affadavits in pursuit of information and hold hearings if necessary with evidence taken on oath where authorities are suspected of stonewalling or destroying evidence.

Above all, he believes it is time to reassert the role of the commissioner as final arbiter of disputes, not a player in an increasingly prolonged process.

"All of my suggestions are about ways to truncate the process," he said.

"We need to avoid public authorities giving shifting reasons for refusals to comply. They will cite commercial reasons, then pledges of confidence, then the public interest.

"They will also put in repeated responses and late responses. It is time to stop them having more than one bite of the cherry. The law is meant to give them an opportunity to respond, not to make several responses."

The commissioner repeatedly refers to public bodies generally, refusing to specify which authorities, but he has had a series of run-ins with the Scottish Government, particularly over the SNP's plans for a local income tax – a case which twice ended up in the Court of Session only to be withdrawn at the 11th hour.

The Scottish Government is promising an update to the FoI legislation and is minded to grant an extension to the time limit on prosecution for destruction of evidence, but it is the lack of action within current laws that has disappointed Mr Dunion.

The Westminster Government is currently consulting with 400 bodies with a view to designating them as liable under FoI rules, but nothing similar has happened here, so the likes of the Convention of Scottish Local Authorities, The Association of Chief Constables Scotland, the Law Society of Scotland or Glasgow Housing Association are under no such warning.

"The view that FoI is an intolerable regulatory burden on authorities turns the clock back 20 years and is not supported by evidence," he said.

"Alternative measures such as codes of practice and voluntary charters have been shown not to work effectively – often because there is no capacity for a commissioner to enforce compliance and hear appeals. Designation is not just about extending the reach of the Freedom of Information Scotland Act, but safeguarding vital rights to information."

Before that legislation was carried out almost a decade ago, and before Mr Dunion had taken on his full powers as commissioner, he handled his first case under previous rules about codes of practice.

It was a demand from Nicola Sturgeon for Reliance, the private company handling prisoner escort duties, to answer questions. Reliance remains exempt, as are privately run prisons, hospitals and housing providers.