Gardai investigating the murder of double agent Denis Donaldson are pursuing a new line of inquiry almost three years after the killing.

The senior Sinn Fein figure, who had been operating as a British spy for 20 years, was found dead in his remote home at Cloghercor, near Doochary in Co Donegal on April 4, 2006.

He had been shot four times in the chest, face, arm and hand in the cottage, situated 8km from Glenties.

Superintendent Eugene McGovern sought and was granted a further adjournment of the inquest for a further year yesterday to facilitate the ongoing investigation.

Supt McGovern told the coroner’s court that since its last sitting eight months ago, gardai had begun pursuing “another avenue of investigation” regarding the death of Mr Donaldson, which was not completed.

He added that the Assistant Garda Commissioner had spoken to the Donaldson family about the new line of inquiry.

He said that while these matters were being advanced, gardai did not feel they would be able to progress the investigation significantly in the short term.

Ciaran Shiels, solicitor for the Donaldson family, said the family was still anxious for the inquest to take place.

He confirmed that the assistant commissioner had met with the Donaldson family and had indicated that another potential avenue of investigation had emerged.

Mr Shiels agreed that gardai should be allowed reasonable time to pursue this line of inquiry but he added that if in a year’s time matters had not been progressed, the family would be pressing for a date to be fixed for the inquest.

Coroner Dr Denis McCauley granted the adjournment, saying that the ultimate desire would be that a perpetrator would be identified and charged.

He said that if the garda investigation was still active in a year’s time he would consider a further adjournment.

Counsel for the Garda Commissioner, Stephen Byrne, acknowledged the forbearance of the Donaldson family for whom the situation became more difficult with each passing year.

The inquest, which opened for the third time yesterday, has now been adjourned until February 2010. Following a previous inquest, Mr Donaldson’s family said their confidence in the garda investigation had been so severely undermined that they had lodged formal complaints.

Among their concerns was whether or not Mr Donaldson had been adequately warned about any perceived threats to his life.

They also had concerns about whether the cottage where he had been living had been under electronic surveillance by gardai.