Scottish police forces have been asked to consider privatising custody services and told to improve cells to take greater account of offenders' human rights.

A report published today by Her Majesty's Inspectorate of Constabulary for Scotland says forces need to review their custody facilities with regard to prisoners' welfare and rights and consult appropriate bodies.

It also recommends that the Scottish Government and individual forces should consider privatising or centralising police custody and think about whether the Scottish Police Services Authority (SPSA) should oversee this.

Such a proposal is likely to fuel controversy in the ongoing debate about the breadth of responsibilities which should be passed to SPSA, the body set up a year ago to oversee back-office functions for all eight forces.

Chief constables have backed the SPSA but warned against drawing too much power to the centre.

The report states: "As a precursor to replacing existing custody facilities, we believe that forces should consider whether centralising or privatising the custody function would offer benefit.

"Certainly as an efficiency measure, centralising provision within and across forces merits consideration (with or without privatisation), as does the possible role of the SPSA in managing or procuring this. There is currently a requirement for police officer involvement in the process of accepting prisoners into custody.

"HMICS would simply offer the Scottish Government and forces the professional view that beyond this role there is no compelling operational reason for the custody and care of people arrested or detained by police to remain within the day-to-day management of police forces."

The report also makes a number of suggestions about how police cells should be configured, including proposing that forces "use microwave sensors" to identify the movement of a person breathing and activate an alarm if there is no movement over a defined period.

The report found that all forces had problems meeting demand for cells at peak times and that many offenders were forced to share cells.

Strathclyde police, Scotland's largest force, was held up in the report as an example of best practice. The force is currently undertaking a 20-year review of custody suites.

Paddy Tomkins, HM Chief Inspector of Constabulary, said: "Our inspection found that the design of force custody suites varied across Scotland, according to age, history and limitations of the site. That's why we've worked to identify good practice and help make sure all forces can learn from the many good examples that exist.

"The standards expected in terms of the duty of care are properly much higher than they were in the times when these facilities were first built - that means adopting higher standards will cost in terms of capital investment.

"Police authorities and central government need to be aware of this when projecting capital spend and, for some, this may mean new ways of collaborating or out-sourcing' will have to be explored.

"We'd like to see a more joined-up approach across Scotland. At the moment it's left up to individual forces to decide when and what changes to make or what bids to make for capital budget."