The "moral case" for invading Zimbabwe has been made but there are too many practical constraints preventing the operation, Liberal Democrat leader Nick Clegg has said.
Mr Clegg made the statement at his first major foreign policy speech, during which he described the kind of 'liberal interventionism' his party would support.
Mr Clegg said the international community has "ample justification to step in" to the country but that practical considerations made it impossible. He did not specify if those related to the continuing campaigns in Iraq and Afghanistan or some other factor.
Instead, he proposed cutting off foreign remittances to Zimbabwe.
Such a move would prove highly controversial even among those groups who want an end to Mr Mugabe's time in power. Foreign remittances - the money sent by Zimbabweans living abroad, provide a vital economic lifeline to those suffering in the country.
"Cutting off foreign remittances is a serious step with serious consequences," Mr Clegg said.
"I know that it would hurt the ordinary Zimbabweans who rely on remittances from friends and family abroad. But the fact remains that access to foreign currency is the only thing that enables the regime to function and therefore the only thing that sustains Mugabe in power."
He continued: "It is now too late for free and fair elections in Zimbabwe. But it is not too late for Britain to act within the EU, the UN and, crucially, with countries in the southern African region to act decisively against Mugabe.
The comments come as events in Zimbabwe reach fever pitch. The opposition Movement for Democratic Change has now stepped out of the presidential elections citing violence and leader Morgan Tsvangirai has taken refuge in the Dutch embassy in Harare.