A Belfast man will today start a High Court action to try and prevent the appointment of Drew Harris as the new Garda Commissioner.

Lawyers for Ciarán MacAirt will argue that giving the former RUC officer the role is “wildly inappropriate” and “a breach of Irish national security.”

Mr MacAirt's grandmother Kathleen Irvine was one of fifteen victims of the 1971 bombing of McGurk's Bar.

He has been campaigning for a new inquiry into the bombing of the Belfast pub, amid claims that British security forces helped the UVF carry out the atrocity.

He has accused Mr Harris of preventing victim’s families from getting to the truth, in his role as head of the PSNI's Historical Enquiries Team.

Ciarán MacAirt, pictured outside McGurk's Bar, is taking the High Court action | Image: YouTube/Ciarán MacAirt

The Belfast man's lawyers will argue it would be "an astonishing breach of Irish National security," to appoint a man they call Britain's most senior counter-insurgency practitioner as head of An Garda Síochána.

Mr Harris was announced as the new Garda Commissioner back in June.

The appointment came following an 'international selection process' by the Public Appointments Service, on behalf of the Policing Authority.

He is set to become the first outsider to be appointed to the top Garda job.