Gordon Brown calls for the UN human rights envoy to return to Zimbabwe
Gordon Brown has described Zimbabwe President Robert Mugabe's regime as a "criminal and discredited cabal" which "should not be recognised by anybody".
He told MPs it had made it impossible to hold fair elections and "state sponsored terror" had put opposition party MDC in an "untenable position".
The prime minister said he would push for more sanctions against the regime.
He said Britain would offer "substantial help" for reconstruction "once democracy has been restored".
Mr Brown told MPs he had spoken to the leader of the MDC opposition, Morgan Tsvangirai, who has pulled out of Friday's election run-off because of pre-poll violence, handing automatic victory to Mr Mugabe.
Mr Tsvangirai has since sought refuge in the Dutch embassy in Harare.
In a Commons statement Mr Brown said Zimbabwe had seen more than 80 killings, 2,700 beatings, the detention of opposition leaders and the displacement of 34,000 people.
"The whole world is of one view - that the status quo cannot continue. The African Union has called for violence to end.
Will you set out a detailed rescue package for the post-Mugabe era, to make it absolutely clear that when Mugabe goes we will do all we can to breathe new life into that country
David Cameron Conservative leader
"The current government, with no parliamentary majority, having lost the first round of the presidential elections, and holding power only because of power and intimidation is a regime that should not be recognised by anyone."
He said on Monday he had talked to UN Secretary General Ban Ki-Moon, to the African Union president, the president of South Africa and Mr Tsvangirai about the situation.
He said the international community had to send a powerful message that it would not recognise "fraudulent election rigging" and "the violence and intimidation of a criminal and discredited cabal".
Liberal Democrat leader Nick Clegg said he hoped the international community would look at "all options available" to put an end to Mugabe's regime and urged the government to allow Zimbabwe's asylum seekers to live and work temporarily in the UK.
Mr Brown said each asylum case was dealt with on an individual basis.
Conservative leader David Cameron welcomed Mr Brown's comments about wider EU sanctions against members of the regime but asked that he make sure "it really happens this time".
Robert Mugabe and his thugs made an election impossible
David Miliband Foreign Secretary
He urged a UN inquiry into abuses of human rights with a view to a possible criminal action later on and asked: "Will you set out a detailed rescue package for the post-Mugabe era, to make it absolutely clear that when Mugabe goes we will do all we can to breathe new life into that country and into those people who have suffered so much."
He also said the government should say it is prepared to withdraw international recognition from the regime.
Later in a separate Commons statement, Foreign Secretary David Miliband said the "only people with any democratic legitimacy" were the opposition MDC party and added: "We do not, repeat do not recognise the Mugabe government as the legitimate representative of the Zimbabwean people."
He added: "The stage was set for the most rigged election in African history. The failure is not of the opposition but of the government. Robert Mugabe and his thugs made an election impossible."
Mr Miliband said it was now for Sadc (the Southern African Development Community) and African Union leaders to meet to establish "a clear framework of engagement".
He also said the UN Security Council would discuss the situation later on Monday - and it was important it worked with Sadc and the AU on the issue.
The Liberal Democrats have called for "foreign remittances" - money sent back to Zimbabwe by Zimbabweans abroad should be stopped as they are a source of funding for the regime.
But Mr Miliband urged the party to stop calling for it, saying the money was vital for suffering Zimbabweans - and dismissed the Lib Dems' call to put pressure on Mozambique and South Africa to cut off electricity supplies.
There has been mounting international criticism of Zimbabwe's government in advance of the run-off presidential election.
But President Mugabe and Zanu-PF blame the opposition for political violence across the country. Mr Mugabe said last week that the MDC would "never, ever" be allowed to rule Zimbabwe.
Zanu-PF also said Mr Tsvangirai had withdrawn to avoid "humiliation".
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