MI5 should provide more precise detail when seeking surveillance warrants in Northern Ireland, a former watchdog said.

The secret service applies to the secretary of state for permission to carry out some of its work and the paperwork was of a high standard, the ex-Intelligence Services Commissioner said.

Warrants are needed for intrusive surveillance of property, either in person or using a monitoring device like a CCTV camera, and have been used to bring charges against suspected dissident republicans.

Retired Appeal Court judge and commissioner Sir Mark Waller said: "My inspection of the Northern Ireland Office [NIO] noted a high standard of paperwork, which I was pleased to note demonstrated the appropriate necessity, proportionality and privacy considerations.

"I did note, however, that submissions from MI5 to the secretary of state for Northern Ireland assumed a certain level of knowledge about the target.

"I would like to see set out in more precise detail the relationship between the subject of the warrant and the relevant terrorist group, as well as the operation's stated aims.

"While I have every confidence that the secretary of state is well versed in the threat picture, I believe this measure would improve independent oversight and will smooth the process of judicial pre-authorisation under the Investigatory Powers Act (IPA)."

Sir Mark was writing in a recently published annual report before his office was dissolved and replaced with an Investigatory Powers Commissioner (IPC).

He recommended subjecting warrants to certain terms in future.

"I am aware, however, of certain legal arguments against this and so expect that this matter will be discussed further with my successor and subsequently the new IPC."

MI5 has scored a number of notable successes against suspected dissident republicans using surveillance.

Seven men were charged with terrorist offences after 70 hours of discussions were taped at a house in Newry, Co Down.

An NIO statement said: "The NIO, like other relevant departments, closely considers the commissioner's recommendations and comments."

On September 1 last year the office of the Intelligence Services Commissioner was abolished and the powers taken over by the Investigatory Powers Commissioner's Office.

IPCO has taken over the inspection and oversight functions and was established under the Investigatory Powers Act.

The law is intended to ensure the powers the security and intelligence agencies and law enforcement use to investigate crimes are used responsibly and proportionately.

A British government spokesman said: "All relevant government departments and the UK intelligence community will consider the comments and recommendations in the report."