Foreign Secretary David Miliband accuses Mugabe of 'sadism' in Zimbabwe

The Foreign Secretary also said South Africa had a 'responsibility' to put pressure on its tyrannical neighbour, whose security forces are intimidating the opposition ahead of a presidential run-off election on June 27.

He said: 'The first thing is to be clear about the sadism, and I use that word advisedly, that's going on in Zimbabwe at the moment.

'People being killed, people being tortured, people being beaten. Election observers being stripped out, election officials being stripped out. It's important that we speak plainly and frankly about that.'

Robert Mugabe attending the burial of Norbert Chingombe a former army general in Harare, Saturday

Foreign Secretary David Miliband vents his opinions on BBC's Andrew Marr show

Mr Miliband said he and Gordon Brown had spoken to the UN Secretary General Ban Ki-moon over the weekend about the need for more election observers to ensure the run-off is not rigged.

'We can raise this at the U.N. and it's right that we do so because the pressure needs to be on absolutely clearly," he said, saying he hoped for more action from the security council.

'Four million refugees will not even have a vote in this election even if they dared to vote. It's important that the international community is clear about its own perspective because that can give confidence to the people in Zimbabwe.'

The veteran Zimbabwean leader, who has ruled Zimbabwe since independence from Britain in 1980, has threatened to go to war to stop a Tsvangirai victory.

The state-run Sunday Mail newspaper said Mugabe told a campaign rally late on Saturday that he was  'prepared to relinquish power to those ZANU-PF officials that uphold the country's independence legacy'.

'This country cannot be sold at the stroke of a pen,' he said, repeating a vow not to let the MDC, whom he has branded as British puppets, rule the country.