The DUP has urged the prime minister to get on with leaving the EU.
It was the first party in Northern Ireland to nominate a candidate for European elections it hoped it would not have to fight.
Diane Dodds is an outgoing MEP and pledged to honour the result of the Brexit referendum.
Leader Arlene Foster said: “We want a very strong message to go back to Brussels and London to get on with leaving the EU.”
Northern Ireland’s three seats in Brussels have historically been divided between the DUP, Sinn Fein and the Ulster Unionists.
Sinn Fein’s Martina Anderson is to run again while veteran Ulster Unionist Jim Nicholson is stepping aside after decades in the European Parliament.
Mrs Dodds said: “We have a parliament that has tried every manoeuvre to try to thwart the will of the people.
“We in this election are asking people to come out to reinforce that message that the UK voted to leave the EU.
“We therefore should leave the EU and we should leave as one nation.
“We want the UK to leave as one and we want our prime minister to get on with the job of doing it.”
Poll results in Northern Ireland have traditionally divided along unionist and nationalist lines.
Mrs Foster said people would want to register their support for the UK’s Union in this election and reiterated the need to deal with the Irish border backstop.