Rebel Labour members have said history will judge the party leadership's failure to back election candidates in Northern Ireland and its threats to expel those standing for the Assembly.
The eight Stormont candidates are being warned of expulsion after deciding to defy the National Executive Committee (NEC).
The NEC pledged to "review" the party's long-standing stance not to contest elections here, but it was not completed before the deadline for candidates to lodge their nomination papers.
Northern Ireland branch official Bikash Chudal said: "Labour Party NEC cannot go against around 2,000 members and supporters of the Labour Party in Northern Ireland.
"Can anyone believe that the party which is waiting for the next Government of this great nation can be so indecisive?
"No, Labour Party NEC and its leaders have no right to be indecisive on Northern Ireland Labour Party issues. History will judge the ability of leadership."
A number of candidates - running under the banner of Northern Ireland Labour Representation Committee (NILRC) - have been sent letters warning them they could be kicked out of the party.
The party branch in Northern Ireland launched a petition seeking public support and took out an advert in the Belfast Telegraph signed by around 1,000 members and supporters, including Baroness May Blood and former Women's Coalition leader Monica McWilliams.
The advert stated: "There are now over 1,700 Labour Party members and registered supporters in Northern Ireland.
"Many more help directly fund the Labour Party through trade union contributions. Despite this, members are currently not allowed to stand for election in Northern Ireland."
But party general secretary Iain McNichol insisted: "We do not stand candidates in Northern Ireland, and (NI members are) not empowered to reverse this position."
He warned the local branch - where membership is said to have more than tripled since Jeremy Corbyn became leader - it is in danger of breaching party rules.
"Attempts such as this to force the hand of the NEC are unlikely to be looked upon favourably. The Northern Ireland (branch) does not have the authority to select candidates and must desist from this course of action," he added.
Historically, Labour's NEC has regarded the SDLP as its 'sister' party in Northern Ireland and declined to run candidates against it.
But Mr Chudal argued: "Who is responsible for this situation? NEC made this problem. Why didn't they give their review decision in time?"
The eight NILRC candidates are: Kathryn Johnston, whose late husband Liam Clarke was political editor of the Belfast Telegraph; Peter Dynes; Brigitte Anton; Emma Hutchinson; Maria Lourenco; Abdo Thabeth, Erskine Holmes, Damien Harris.