Former Northern Ireland First Minister Lord David Trimble | Charles McQuillan/Getty Images David Trimble to take UK government to court over Irish backstop Ex-Northern Ireland first minister says plan is in breach of Good Friday Agreement.

LONDON — A former first minister of Northern Ireland is to take Theresa May's government to court, claiming that her Brexit deal is in breach of the Good Friday Agreement.

David Trimble, a Nobel Peace Prize-winner who played a major role in the 1998 peace deal, plans to launch judicial proceedings in an attempt to force May to drop the backstop plan for avoiding a hard border between Northern Ireland and the Republic of Ireland.

Many Northern Irish unionists are deeply opposed to the backstop because, if enforced, it would mean Northern Ireland operating under certain EU rules, separate to the rest of the U.K., creating what they fear would be an economic border in the Irish Sea.

Trimble, a former leader of the Ulster Unionist Party, was the inaugural first minister of the devolved Northern Ireland executive, serving from 1998 to 2002. May's parliamentary majority is guaranteed by a rival unionist party, the Democratic Unionist Party, which is also deeply opposed to the backstop.

The planned legal action was announced in a statement from the pro-Brexit Global Britain think tank, which said that Trimble wants the backstop in the Withdrawal Agreement replaced with "alternative arrangements" as set out in a paper endorsed by Conservative Brexiteers last month called "A Better Deal, A Better Future."

The alternative plan to avoid a hard border involves an "interim free trade agreement" between the U.K. and EU covering agriculture and goods and "border facilitations."