A member of the Labour Party in Northern Ireland (LPNI) has been expelled by the party's ruling executive for standing on a different ticket in the assembly election.
Donal O'Cofaigh is the Cross-Community Labour Alternative candidate for Fermanagh & South Tyrone.
He was expelled last week along with LPNI activist, Adam Gannon, who had been campaigning for him.
Labour said it is against the rules to be a member of another political party.
Mr O'Cofaigh is a former Sinn Féin councillor who also stood as a candidate for the Socialist Party in 2011, before joining the Labour Party last year.
He told the BBC he had wanted to run on a Labour Party NI ticket this year, but due to party rules, he could not.
People in Northern Ireland have been allowed to join the Labour Party since 2003 - but it does not allow candidates to stand in Northern Ireland elections.
However, the party has begun a consultation process to consider whether they should contest Northern Ireland elections, according to BBC News NI political correspondent, Stephen Walker.
He reported that Labour is to discuss the issue with a series of groups over the coming weeks, including the Northern Ireland Constituency Labour Party, affiliated trade unions, the Irish Labour Party, the Co-operative Party and the SDLP.
Last year, eight candidates defied the party's hierarchy and ran under the banner 'Northern Ireland Labour Representation Committee' (NILRC).
Mr O'Cofaigh said he approached Cross-Community Labour Alternative, who then allowed him to run as a candidate under their party banner in March's election.
Under section 2 of the Labour Party membership rules, it states: "A member of the party who joins and/or supports a political organisation other than an official Labour group or other unit of the party... shall automatically be ineligible to be or remain a party member."
A Labour spokesperson said as the matter was internal it could not go into detail, adding: "It is against Labour Party rules to be a member of another political party.
"Where there is evidence of a member being a member of another political party, that member will be auto-excluded."
It is understood Mr O'Cofaigh and Mr Gannon intend to appeal the decision.