BELFAST (Reuters) -Northern Ireland's Democratic Unionist Party (DUP) named Jeffrey Donaldson as its new leader on Tuesday, the third person in a tumultuous few weeks to lead the British province's largest party during crucial post-Brexit talks.

       Lawmakers in the pro-British party ousted then leader and the province's first minister Arlene Foster in late April in favour of Edwin Poots, who stepped down last week after just three weeks in the job.

       Donaldson has pledged to pressure the British government to ditch post-Brexit trade rules agreed with the European Union that effectively treat Northern Ireland as part of the EU for customs purposes under a tailor-made protocol.

       His unopposed candidacy will be formally ratified by party officials next week.

       "I will be speaking with the (British) Prime Minister at the earliest opportunity to emphasise that it is not realistic to expect stability when every unionist representative in the devolved institutions opposes the Northern Ireland Protocol," Donaldson said in a statement.

       "The Government and those who claim to be protectors of peace and stability, must step up and deal with the protocol in a manner which respects the constitutional and economic integrity of the United Kingdom."

       (Reporting by Amanda Ferguson in Belfast and Padraic Halpin in Dublin; Editing by Jon Boyle and Catherine Evans)