Mugabe won a landslide victory last month in a vote that was boycotted by opposition leader Morgan Tsvangirai and denounced by Western nations as violent and unfree. Tsvangirai's Movement for Democratic Change has refused to recognise the result.

"The 27 July, 2008 elections were not free and fair and did not represent the will of the people of Zimbabwe," the Zimbabwe Congress of Trade Unions (ZCTU) said in a press release.

The ZCTU, an ally of Tsvangirai's MDC, said mediation of preliminary talks between the MDC and Mugabe's ruling ZANU-PF should be expanded beyond South African President Thabo Mbeki, who is overseeing the negotiations.

The federation suggested that a retired African president should enter the process as a full-time mediator.

The ZCTU has in the past staged nationwide strikes and job walkouts to protest the government's policies. But Wednesday's statement made no mention of industrial action.