Paul Kenny, general secretary of the GMB, said many of his union's members did not understand why Gordon Brown wasn't being more proactive in tackling current problems such as the rising price of energy, accusing him of constantly reacting to events after they happened.

The GMB will debate calls to disaffiliate from the Labour Party at its annual conference in Plymouth next month in the latest sign of tension between the Government and trade unions.

Mr Kenny said he did not believe the GMB will vote to sever its links with the party, although he admitted his members were feeling "angry and disillusioned" with the Government.

The question now being raised was whether the public had taken a conscious decision not to support Mr Brown, the GMB leader told PA.

Mr Kenny said his members were more angry with the leadership of the Government, including Mr Brown, than with the Labour party, and he believed the GMB would find itself in the political wilderness if it formally split from Labour.

"I am not advocating disaffiliation, but I acknowledge there is widespread concern and dismay about the direction, policies and lack of action by the Government.

"A lot of my members say the Government seems to be reactive rather than proactive. They don't understand why we export gas to Belgium in the summer and buy it back later, at a more expensive price, just because we don't have enough storage facilities. That is the economics of the madhouse.

"They don't understand why something hasn't been done about the obscene City bonuses which have helped fuel the housing slump.

"The Government doesn't appear to be addressing the basic issues."