Image copyright Getty Images Image caption After initial denials, it has been confirmed that undercover police deployed by Scotland Yard worked in Northern Ireland, without the knowledge of local officers

Northern Ireland's justice minister has backed calls for an extension to an inquiry into controversial undercover police units working for Scotland Yard.

The Pitchford Inquiry is investigating allegations of misconduct by undercover officers in England and Wales.

Some are accused of miscarriages of justice and having sex with women who did not know they were police officers.

Justice Minister Claire Sugden said the units' activities may have implications for investigations in Northern Ireland.

Met apology

It has been revealed that the Metropolitan Police has contacted the family of at least one Troubles murder victim to say an undercover officer infiltrated a protest about the killing.

After initial denials, it has been confirmed that members of the units worked in Northern Ireland, without the knowledge of local police.

Last year, the Metropolitan Police was forced to issue a public apology after it was revealed that some of the undercover officers infiltrated environmental pressure groups by tricking women into sexual relationships.

Image copyright Image courtesy of The Guardian Image caption Mark Kennedy, one of the former undercover officers about whom the Met apologised, made contact with environmental activists in Northern Ireland

Prime Minister Theresa May, in her previous role as Home Secretary, established an inquiry chaired by Lord Justice Pitchford to examine allegations about the Special Demonstration Squad and the National Public Order Intelligence Unit.

But she limited its scope to England and Wales.

She refused a request from the Scottish government for the terms of reference to be extended.

Now the BBC has established that the Stormont justice minister also asked for the inquiry to be extended to include Northern Ireland.

'Relevant material'

That is despite the fact it has been confirmed that a number of the undercover officers worked in Northern Ireland, without the knowledge of the Royal Ulster Constabulary (RUC) or Police Service of Northern Ireland (PSNI).

The BBC revealed last year that one of the officers was Mark Kennedy, who is known to have attended at least two meetings of environmental activists in Belfast in 2005.

In a letter sent in June when Mrs May was still at the Home Office, Justice Minister Claire Sugden MLA said the PSNI had examined thousands of Scotland Yard documents after being told there may be material relevant to Northern Ireland.

The letter said the Metropolitan Police has "contacted the family of at least one murder victim... to inform them that their officers were present at protest activity relating to the murder".

It added that the Met "plans to contact another family for a similar reason".

Ms Sugden said it was possible that operations conducted by the undercover units, or any material they gathered, could have implications for police investigations and inquests in Northern Ireland.

Image caption Claire Sugden said the undercover units' activities could have implications for investigations being conducted by the PSNI

As a result of those potential implications, she said it was imperative for the inquiry to follow the evidence trail - in any jurisdiction.

Activists and campaigners in Northern Ireland who claim they may have been spied on by the undercover units also want the terms of reference of the inquiry to be extended.

'Public concern'

A lawyer acting for a number of them has written to the prime minister, claiming a failure to extend the investigation would be a breach of their human rights.

"It would be a question of the utmost public concern if an undercover officer were effectively permitted to operate without justification, authorisation or oversight in Northern Ireland," said solicitor Darragh Mackin.

"It would not be rational for the UK government to conclude that there was a need for a judge-led inquiry into these allegations in England and Wales, but no need for an inquiry into the same allegations, involving the same undercover officers, in Northern Ireland."

The government has not yet responded to the letter, which was sent on 10 June.