An inquest into the death of Denis Donaldson, who was shot dead in Co Donegal in April 2006, has been adjourned for the 12th time.

Questions have also been raised by his family’s solicitor about the adequacy of the garda investigation into his death.

Mr Donaldson was killed in the remote cottage he had been living in near Glenties following his disclosure as an MI5 agent in 2005.

A preliminary inquest into his death was opened in Letterkenny in 2007, but was adjourned because of the ongoing garda investigation into the case.

The request for the latest adjournment was made by Superintendent Michael Finan.

He said further information had been requested by the Director of Public Prosecutions since the last hearing.

Supt Finan said a file has been with the DPP for 11 months and the new information requested was of a technical nature, which would take time to consider.

The request was made last May and was being supplied right up to this week, he said.

Solicitor for Mr Donaldson, Ciaran Shiels, said it was hugely disappointing that all the information had not been fully considered and a decision or direction given.

Barrister for An Garda Síochána, Stephen Byrne, said he understood the family’s frustration, but hoped the family accepted that gardaí were doing all they can to ensure the DPP has all the information necessary to come to a decision on whether to prosecute.

Mr Shiels said if there is no criminal prosecution, the family felt that the coroner should inquire into the garda investigation into Mr Donaldson’s murder.

However, Mr Byrne said this was beyond the remit of the coroner’s court.

Mr Shiels said the family wants to see the garda file and to know as much of the truth as can be known about the murder of their father.

They felt the garda investigation is very much incomplete.

He said they have not questioned Mr Donaldson’s handler, who Mr Shiels referred to as Lenny, or those who controlled the handler.

He also claimed they had not looked at the ongoing contact they had with Mr Donaldson in Donegal.

Mr Shiels said he was not there to specifically criticise gardaí, but said the coroner may have to look beyond the garda file to avenues of investigation that were not pursued.

He also said gardaí had told his clients that there was very limited contact between Mr Donaldson and gardaí while he was in Donegal.

Coroner Dr McAuley asked both legal teams to make further written submissions to him regarding the scope of the inquest, if they wished, and adjourned the hearing until 27 March 2014.