Morgan Tsvangirai will be sworn in today as Zimbabwe's new Prime Minister. But neither he nor his party, nor the millions who voted for them in last year's elections, should be in any doubt about who wields real power in the country they have tried and so far failed to change. That man is still Robert Mugabe.

It is now ten months since Mr Mugabe forced Mr Tsvangirai to withdraw from a second-round presidential vote with a campaign of murder and intimidation. Not once in that time has he relaxed his control over Zimbabwe's police or security services, or the process leading to the formation this week of a so-called unity Government.

This is not a government of unity, but of coercion and co-option. By joining it, the Movement for Democratic Change (MDC), which Mr Tsvangirai has led for ten years at great personal risk, is in danger of legitimising the very tyranny it sought to end. MDC officials are to be installed in 13 ministries, but none will give Mr Tsvangirai the power to enforce as well as write new laws, let alone rebuild a country brought to its knees by violence, disease and artificial famine.

Mr Tsvangirai has named his chief negotiator as the new finance minister while allowing the architect of Zimbabwe's economic collapse, the governor of the national Reserve Bank, to remain in post. He will have an appointee in the vital home affairs portfolio, controlling the police - but so will Mr Mugabe. And Mr Tsvangirai himself will have a new office, in the same building as Mr Mugabe's. The man who should have been the democratically elected President of Zimbabwe since last April is instead the junior partner in a shameful arrangement guaranteed only to perpetuate the corruption of an elite that is preparing to feast on lobster for Mr Mugabe's forthcoming birthday while more than half his subjects depend on food aid to survive.

It has taken a decade of cruel mismanagement to turn this country of extraordinary natural wealth into a humanitarian disaster. More than 3,400 people have died of cholera since August, excluding those uncounted because they live in rural areas beyond the reach of aid agencies or government. Only 6 per cent of Zimbabweans have jobs. Most of those who do not subsist on ground maize imported from South Africa. Hyperinflation has sidelined the local currency in favour of barter and scarce US dollars.

Mr Tsvangirai's first international appeal will be for a rapid increase in the amount of foreign aid reaching Zimbabwe. For charities and individuals there is a case for seeking new ways of channelling aid to ministries and city councils - such as Bulawayo's - that are MDC controlled. The need is acute and there is a risk of the MDC being blamed by the desperate and the disenchanted if living conditions fail to improve on Mr Tsvangirai's watch. But the graver risk is of fresh aid merely shoring up the Mugabe kleptocracy.

Donor governments must, therefore, be clear about their ground rules. The condition for releasing the large-scale, co-ordinated Western state aid that Zimbabwe so urgently needs must be the removal of its illegitimate and murderous leader and his henchmen, and their replacement with a genuinely new government that reflects the clearly expressed desires of its people.

An opposition politician who has endorsed the lopsided power-sharing deal told an audience in Davos recently that it was “not for Britain or America to judge our agreement” but only “to support what we try to do”. South Africa has justified its “quiet diplomacy” towards Zimbabwe in similar terms, and the results have been disastrous. African solutions to Africa's problems are the right ones only if they work. What Zimbabwe needs is a solution the whole world can agree on, and that is the removal of Mugabe.