Published Tuesday, 13 November 2012
Edward Devenney, 30 and from NI, pictured at an earlier court appearance. (© PA)
Petty officer Edward Devenney, 30, admitted the charge of gathering "crypto material" as he was due to stand trial at the Old Bailey in London on Tuesday.
The breach of the Official Secrets Act is said to have occurred sometime between 18 November last year and 7 March this year.
Devenney also admitted a charge of misconduct in a public office, in relation to a meeting with two people he thought were from the Russian Secret Service.
During the meeting, they discussed information relating to the movement of nuclear submarines - but the two men were actually British secret agents.
The submariner, who was arrested in Plymouth in March this year, denied a second count of communicating information to another person.
That charge will not be pursued by prosecutors.
Devenney will reappear at the Old Bailey for sentencing next month, with parts of the hearing to be held in secret due to the nature of the case.
"Your sentence will be adjourned to 12 December, when I will hear all the matters and consider them all," Mr Justice Saunders told him.
"Until then you are remanded in custody."
© UTV News