Holyrood's Justice Secretary has pledged there will be "rapid intervention" if performance drops below standard at any of Police Scotland's call handling centres.

Michael Matheson also announced the centres, which deal with half a million 999 calls and 3.24 million 101 calls a year, will be subject to unannounced inspections by HM Inspectorate of Constabulary in Scotland (HMICS) while an ongoing restructuring programme is carried out.

The Scottish Police Authority has been monitoring performance at the call handling centres on a weekly basis, and the Justice Secretary stressed: "In future any dip in performance such as experienced in Bilston Glen earlier this year will become quickly apparent and will trigger rapid intervention."

The Scottish Government ordered an urgent review of call handling north of the border after it emerged that officers took three days to respond to reports of a car crash on the M9 near Stirling in July which claimed the lives of Lamara Bell and John Yuill.

The report, by HMICS, includes "some hard messages for Police Scotland", Mr Matheson accepted.

It said staff levels at the Bilston Glen contact, command and control centre - where the initial call regarding the fatal crash was received - were insufficient and also highlighted concerns about training and IT systems.

Mr Matheson told Holyrood that Police Scotland had assured him the 30 recommendations for change in the report would be implemented in full.

While he said "significant progress" had been made since the time of the M9 crash, he added the review "gives a clear direction" to both Police Scotland and the Scottish Police Authority about where further improvements are needed.

The Scottish Government has already announced control rooms in Aberdeen and Inverness will stay open for longer than originally planned, to allow for a new main centre in Dundee to become fully operational.

Mr Matheson said that while performance at the call handling centres had been "stabilised" there are issues that require to be addressed "before the remaining phases of the change programme are progressed".

The Justice Secretary said: "I have discussed this with Andrew Flanagan, the chair of the SPA, and Police Scotland. They have confirmed that independent experts will be brought in to provide strong assurances before any decision is considered regarding the implementation of proposed changes to Aberdeen, Dundee and Inverness centres."

He also stated: "Police Scotland will establish a reference group of senior independent change and call handling professionals who will provide ongoing oversight and advice as the restructuring process progresses.

But Labour's Graeme Pearson said the report was "damning".

"The litany of failures listed in the report are extraordinary," he told MSPs.

"IT systems offering only basic functionality with questionable stability, a lack of resources for front line staff, weak local management, inadequate oversight of call centre rationalisation, the narrow approach to the scrutiny of major projects by SPA and Police Scotland, no framework to measure stated benefits, key staff on the project board lacking experience and training, a lack of staff and those who are there reporting low morale."

He said the Justice Secretary had previously blamed the M9 tragedy on an individual failure, rather than a lack of resources.

"We now know this is completely false," Mr Pearson added, as he called for Mr Matheson to apologise to the families of Ms Bell and Mr Yuill.

Conservative Margaret Mitchell said the report had revealed "a system in chaos".

She added: "There is clearly a huge disconnect between what is happening in practice and what should be happening in call centres.

"Given all we've already heard on this matter, what possible confidence can the general public have that call handling in Scotland is fit for purpose, and history won't be repeated for other families like the relatives of Lamara Bell and John Yuill?"

Liberal Democrat leader Willie Rennie said: "It is a shocking indictment of the Scottish Government that it took tragic deaths before the problems at police call centres were taken seriously."

He urged the Government to now agree to a "fuller inquiry into the whole of Police Scotland".