Labour leader Ed Miliband has been invited to meet union leaders to discuss his plans to change the way union members affiliate to the party.
His proposed reforms have caused dismay in union circles and warnings that Labour will lose millions in affiliation fees.
Labour MP Ian Lavery has described the change as the “biggest political gamble” in the history of the party.
The Trade Union and Labour Party, made up of the 15 trade unions that are affiliated to the Labour Party, has invited Mr Miliband to a meeting at the TUC Congress in Bournemouth next month.
The Labour leader is addressing the conference in what will be his first speech to such a large gathering of union activists since he announced the reforms.