(This March 1 story corrects paragraph 2 to say trawlers seized by Irish Naval Service not Coast Guard)

Ireland's Prime Minister (Taoiseach) Leo Varadkar speaks at a European Financial Forum event in Dublin, Ireland February 13, 2019. REUTERS/Clodagh Kilcoyne

DUBLIN (Reuters) - Ireland’s Prime Minister Leo Varadkar promised on Friday to resolve a legal “anomaly” that led to the seizure of two small fishing boats from Northern Ireland and drew angry denunciations from pro-British politicians.

A 60-metre armed Irish Naval Service vessel on Thursday impounded two trawlers registered in the British region of Northern Ireland for fishing illegally inside Ireland’s six-mile (9.6 km) territorial limit.

Northern Ireland’s Democratic Unionist Party, a close ally of British Prime Minister Theresa May, reacted angrily, with deputy leader Nigel Dodds on Thursday describing the incident as “outrageous... heavy-handed tactics”. Dodds also accused the Irish government of using it as a “bargaining chip on Brexit”, something the Irish government denied.

The owners of the trawlers pleaded guilty to breaching fishing regulations at Drogheda District Court on Friday but a judge decided to release them without levying a fine, the BBC reported. A court service official declined comment.

An informal bilateral agreement had allowed fishermen from Ireland and Northern Ireland to fish inside the six-mile limit of each others’ jurisdictions, but it was struck down by the Irish Supreme Court in 2016 and Ireland has yet to approve replacement legislation.

As a result Irish fishermen can legally fish along Northern Ireland’s coast but Northern Ireland fishermen are prohibited from fishing along the coast of the Republic of Ireland.

“I think we can have that law changed and that anomaly, if you like, corrected, and we can do that in the next couple of weeks,” Prime Minister Varadkar told LMFM Radio, saying legislation had got stuck in the upper house of parliament, which Varadkar’s government does not control.

But while Ireland’s Minister for Agriculture, Food and the Marine Michael Creed told RTE radio on Friday that the issue had “zero to do with Brexit,” Varadkar linked the dispute with Britain’s post-Brexit plans for its fisheries and whether or not these it will stay party to the London Fisheries Convention, which governs fishing rights in coastal waters off Western Europe.

“Obviously it would be useful to know from the United Kingdom side that they are not going to pull out of that London Convention,” he said.

“It would be unusual to change our law only to find out that the situation on the other side changed.”

Britain’s withdrawal agreement, which has yet to be ratified by the British parliament, says the two sides would try to agree on the future of fisheries by July 2020, during the transition period after Brexit, to form part of an eventual new EU-UK trade deal.