An anti-globalisation activist was followed to Northern Ireland by an undercover police officer, the High Court heard today.
Counsel for Jason Kirkpatrick claimed further incidents of spying took place as he launched a legal bid to have a public inquiry extended beyond England and Wales.
Concerns were also raised over any role played by operatives in so-called legacy cases stretching back to the Troubles.
A probe chaired by Lord Justice Pitchford is examining allegations of wrongdoing by officers attached to the Metropolitan Police and the National Public Order Intelligence Unit.
Undercover operatives were deployed to infiltrate alternative movements, from anarchists to environmental demonstrators.
The inquiry was launched following scandals involving officers and women tricked into relationships.
One of the former undercover officers at the centre of the controversy, Mark Kennedy, is alleged to have operated in Northern Ireland alongside environmental campaigners and anti-globalisation demonstrators in 2005.
Mr Kirkpatrick has now commenced proceedings in an attempt to have the Pitchford inquiry widened out to include Northern Ireland.
He is seeking to judicially review the British Home Secretary for refusing to extend its scope.
At a brief hearing in Belfast today, barrister Jude Bunting described his client as an activist and protestor who is already a core participant at the inquiry.
"His case is he was followed to Northern Ireland on a number of occasions by an undercover police officer," Mr Bunting said.
It was also confirmed that the failure of the NI Secretary of State to establish a similar probe is also being challenged.
Mr Bunting contended: "This type of illegality is considered sufficient to set up an inquiry in England and Wales.
"Why is the same illegality not sufficient to set up an inquiry here?"
Following preliminary submissions Mr Justice Maguire adjourned the case to a later date for further argument.
Outside court Mr Kirkpatrick's solicitor stressed the position taken by Stormont Justice Minister Claire Sugden.
Darragh Mackin of KRW Law said: "Our client seeks to rely on the fact that the Minister for Justice has concerns that these officers acted without accountability in this jurisdiction.
"We further mirror the concerns that it remains an unknown the role these officers played in various legacy-related cases, and it is essential in ensuring accountability that (any) role is investigated."