LABOUR HQ in London is to probe allegations of misconduct which last week led to resignations from the party's Northern Ireland executive.
Eight members of regional Labour Party resigned from its ruling committee after claiming some members supported other parties.
Among those quitting the regional executive are its former chair Anna McAleavy and vice-chair Damien Harris.
They claim a "small minority" of members were supporting other political parties, contrary to the Labour rulebook.
However, complaints have subsequently been made about how the regional executive was being run.
Labour's head of internal governance Claire-Frances Fuller wrote to members to notify them of the investigation into "all allegations and complaints made".
She said that several members who resigned last week "made serious allegations of breaches to Labour Party rules in a collaborative resignation statement" but noted that the party received additional complaints involving "allegations of misconduct and improper behaviour relating to the running of the executive committee".
Ms Fuller said that none of the allegations related to financial misconduct and so the treasurer would remain in post.
