Robert Mugabe’s ruling party today accused Morgan Tsvangirai, the Zimbabwean opposition leader, of treason and of working with Britain to oust the President from power.

Patrick Chinamasa, the Justice Minister, said he had seen correspondence showing that Mr Tsvangirai's party, the Movement for Democratic Change (MDC), had asked Gordon Brown to depose Mr Mugabe and install him as President.

“It is clear from the correspondence that Tsvangirai along with Brown are seeking an illegal regime change in Zimbabwe and on the part of Tsvangirai this is treasonous,” Mr Chinamasa said today.

“There are no doubting consequences for acting in treasonous manner."

The allegations came hours after Mr Brown used a speech at a special Africa meeting of the United Nations Security Council to criticise the Zimbabwean authorities for delaying the results of a presidential election last month.

Knox Chitiyo, a Zimbabwe expert and head of the Africa programme at the Royal United Services, told TimesOnline that Mr Tsvangirai's life would be at risk if he returned to Zimbabwe from Botswana, where he is based.

“The big question is whether he will come back to Zimbabwe,” he said. “If he does the Zanu (PF) will probably charge him. They’ll arrest him and put him on trial and then say because he’s accused of treason there’s no point in having a presidential runoff. The consequences of treason are very severe.

“It’s part of an overall strategy to discredite, demoralise and marginalise the MDC.”

Mr Brown told yesterday's summit of the United Nations and African Union: “No one thinks, having seen the results of the polling stations, that President Mugabe has won."

Today the US Ambassador to Zimbabwe added to the chorus of international criticism of the Zimbabwean Government's conduct since the elections, accusing it of murdering opposition supporters, abducting them and forcing them from their homes in a spate of violence in rural areas.

“There is growing evidence that rural communities are being punished for their support for opposition candidates,” Ambassador James McGee said. “We have disturbing and confirmed reports of threats, beatings, abductions, burning of homes and even murder, from many parts of the country."

Mr Tsvangirai’s MDC accuses Mr Mugabe of organising a violent militia crackdown to help him to steal the March 29 elections, in which his Zanu (PF) party lost control of Parliament for the first time in his 28-year rule.

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