The immediate future of Zimbabwe's unity Government is in doubt after Morgan Tsvangirai accused President Robert Mugabe's Zanu-PF of being "dishonest and unreliable".

Mr Tsvangirai, the Prime Minister and leader of the Movement for Democratic Change (MDC), said that his party would disengage from the country's troubled unity Government until outstanding issues in the deal were resolved. The party was suspending co-operation, but not “pulling out officially”.

The latest crisis to hit the Government has been triggered by the arrest and trial of a top MDC official, who faces treason charges on what are seen as trumped up coup allegations.

“It has brought home the reality that as a movement we have an unreliable and unrepentant partner in the transitional Government,” he told a news conference. “Until confidence has been restored we can’t continue to pretend that everything is well.”

Mr Tsvangirai said that the freeze would continue until there was a resolution of the dispute over Roy Bennett, who has been named Deputy Agriculture Minister but not sworn in. A feisty white Zimbabwean whose farm was confiscated by Mr Mugabe, he was taken back into detention this week and is now due to appear in the High Court on Monday.

Today’s move demonstrates deep unhappiness within the MDC over the coalition. However, Mr Tsvangirai, who has limited power, has repeatedly said that he sees it as the only way to ensure Zimbabwe’s future and again stopped short of bringing down the Government by pulling out altogether.

Critics say that the policy is the worst of all worlds and simply demonstrates the MDC’s weakness in the face of ZANU-PF intransigence. Others say it is designed to bring outside influence to bear on Mr Mugabe, who himself faces pressure from hardliners within the ruling clique.

“The boycott decision demonstrates to some extent the limited options which the MDC has in trying to pressure Mugabe, but the decision will pressure regional observers to try and intervene,” said Mike Davies, an analyst with the UK-based Eurasia Group.

ZANU-PF's reaction underlined tensions within the coalition. “If MDC wants to disengage . . . we don't have a problem with that,” said Ephraim Masawi, a ZANU-PF spokesman. “We were having problems with MDC, working together. We have been trying but it was not easy.”

Mr Tsvangirai and Mr Mugabe entered the unity Government in February after two violence-plagued and widely disputed elections left the country at a political stalemate and in danger of serious violence.

Neighbouring countries in the Southern Africa Development Community, led by South Africa, brokered the deal, but it has been plagued by problems since its inception.

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