But the head of the Northern Ireland police service did not apologise for the move during a policing board meeting on Thursday.

The Northern Ireland Audit Office report, which was published on Wednesday, revealed that more than £106m has been spent by the PSNI on agency staff since 2004.

The Royal Ulster Constabulary (RUC) officers retired with generous severance packages as part of Lord Patten's scheme to overhaul the force and introduce more Catholics to policing following decades of conflict in Northern Ireland.

Since then, almost a fifth of retirees have been re-employed - four for longer than seven years and others re-employed within three months of leaving.

At the policing board meeting Mr Baggott faced some tough questions with his force accused of having a culture of withholding information.

SDLP Policing Board member Conall McDevitt has asked the Chief Constable to apologise for how the policy had been handled in the last ten years.

He said the auditors' report told the story of a service that was a "closed shop" and had confirmed suspicions that board members and even senior PSNI officers were being kept in the dark over recruitment decisions.

Both Matt Baggott and his predecessor Hugh Order were accused of keeping the board in the dark at the meeting.

Of course I regret that has had an impact on public confidence and I regret that at the time there wasn't a tighter scrutiny.

Chief Constable Matt Baggott

Mr Baggott did not apologise but did acknowledge what he described as the "corporate grip..not being tight enough" and that not all the posts filled by former RUC officers were justifiable.

"I understand entirely how people can perceive it (as) against the spirit of Patten and we need to look at our own accountability to the board again," Mr Bagott said.

He said that the audit report set out that there had been value for money, the law was complied with and that "there may be a difference about the way the contracts were managed but again the PSNI view would be that it was in accordance with the practice at the time."

Sinn Féin MLA Gerry Kelly welcomed that the Chief Constable accepted a lack of accountability in the way former officers were rehired but said more answers were needed.

"The talk about corporate responsibility- actually individuals were involved in this and I asked today who are the people responsible for this?"

He said he hoped the public accounts committee would probe the issue further.

"Whoever is responsible for this type of practice over this very long period and the damage it has done to policing, I think we will have to look at their position if they are still in the PSNI."

DUP member of the policing board, Jonathan Craig praised the Chief Constable for taking a very "sensible line" in admitting financial failings within the report.

"There was never a need for a PAC report, if he had have dealt with the policing board appropriately and handed over this information over sooner but he did go on to explain some physical reasons why he hadn't got this information at the time," he said.

He praised Matt Baggott for taking on board these "thorny issues" and attempting to bring financial accountability to the PSNI.