Two of Britain's biggest unions have agreed to start merger discussions in a move that could lead to the creation of a 2.5 million member "super union".
Derek Simpson has been holding meetings on the issue
Amicus and the Transport and General Workers Union (TGWU) are also to invite the GMB to join in the talks.
Amicus boss Derek Simpson said the merger would create a "major force" to protect working people's interests.
The TGWU's Tony Woodley said it was an "historic opportunity" for unions to grasp the industrial agenda.
GMB general secretary Kevin Curran said no decision on merger talks could be taken until the union's executive meets.
He added that he recognised the benefits of a merger but the executive ruled out any such move last year.
Tony Woodley meanwhile said: "We could now put behind us pointless inter-union competition and focus on fighting for our members in the workplace as one powerful union.
"Today's announcement is a message of hope for every worker who needs strong trade unionism, and a warning to employers that we intend to match the power of capital with the power of united labour."
Any merger would have to be approved by the unions' executives and their membership.
Along with the GMB and Unison, the TGWU and Amicus worked closely together in the last year to hammer out the Warwick Agreement - a 56-point deal with Labour's leadership over equality at work, holidays and pensions.
Amicus represents skilled, technical and industrial workers while the 615,000-member GMB describes itself as "Britain's general trade union".
Unison, currently the biggest union, represents many of Britain's public sector employees.