"Our state media remains partisan and prejudiced, freedom of association is not yet a right that all can enjoy."

'Political persecution'

Tsvangirai, the former opposition leader, brought his Movement for Democratic Change (MDC) party into a coalition government with Mugabe in February to end the country's long political deadlock and economic collapse.

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He said progress was "being undermined by those that are threatened by the democratic changes contained in the global political agreement"

"Our members continue to be the victims of political persecution,'' he said.

Despite the tensions threatening the unity government, Tsvangirai has shown no sign that he will pull his party out of the coalition in protest.

He said there were limitations to what he could do as prime minister in the coalition government with an uneasy sharing of power.

"We are in a coalition with [Mugabe's] ZANU-PF," Tsvangirai said.

"The MDC is in government but we are not the government

"Those in government will tell you this government is walking on a thin thread."