LONDON - Zimbabwean expatriates in London jeered Prime Minister Morgan Tsvangirai when he urged them to return home to help rebuild the country's ruined economy after a decade of crisis.

Tsvangirai, touring Europe and the United States to garner financial support for Zimbabwe, was booed and heckled during a speech in London when he said: Zimbabweans must come home.

People listening to the speech gave him a thumbs down sign and chanted Mugabe must go before a priest appealed for quiet.

After a disputed presidential election in 2008 which Tsvangirai contested, he joined a unity government with President Robert Mugabe in February.

When Tsvangirai spoke of the country's progress towards peace and stability, most of the audience of several hundred Zimbabweans erupted, saying it was still too dangerous.

I did not say you must pack your bags and go back tomorrow, he said in response to the boos at Southwark Cathedral in London. Before speaking, he was welcomed with loud cheers and ululations.

The once-prosperous country has endured a 10-year economic battering that has left more than half of its people surviving on food aid and forced a quarter to go abroad as economic refugees.

Tsvangirai warned the country needed support from the international community and from Zimbabwean professionals living overseas to avoid sliding back into chaos.

His government says Zimbabwe requires $10 billion to rebuild the economy, wrecked by years of recession and hyper-inflation.

Many in the audience said afterwards that they would only go home if Zimbabwe becomes safer and there are more jobs.

We need to know if the situation has improved in terms of career prospects and security, said Preston Kandayi, 32, who left for Britain 10 years ago because there were no jobs.

Inflation has been helped by the adoption of the U.S. dollar, replacing the Zimbabwe dollar.

Tsvangirai earlier met British Foreign Secretary David Miliband and business leaders to discuss ways to attract more foreign investment and restore prosperity.

His country is in desperate need of investment and economic development, Miliband said in a statement.

Britain's Africa Minister Mark Malloch-Brown, however, said it was too soon to lift sanctions against its former colony.

We will not lift the bulk of these measures until we are convinced that Zimbabwe's transition to democracy has reached a point of no return, he wrote in the Times newspaper on Friday.

Virgin Group's Richard Branson said Zimbabwe was at a critical turning point and needed international support.

I believe continuing to punish the whole country because of the behaviour of a handful of people would be a mistake, he told Reuters in a telephone interview.

(Additional reporting by Avril Ormsby and Peter Griffiths; Editing by Matthew Jones)