The Foreign and Commonwealth Office has told leading British companies that they should continue to operate in Zimbabwe despite political pressure on them to withdraw.

Both Gordon Brown and Lord Malloch-Brown, the Foreign Office Minister, have questioned whether companies should still be operating in Zimbabwe amid concern that they could be helping to prop up the regime of Robert Mugabe.

The French Foreign Ministry said yesterday that European governments were considering widening a visa ban and asset freeze on members of President Mugabe's entourage.

A number of large corporations have contacted the Foreign Office in the past week to check the latest advice following the statements by the Prime Minister and Lord Malloch-Brown but were told that nothing had changed.

One businessman said: “We were told not to leave Zimbabwe and to take no action as long as there were no ethical trading issues. The politicians appear to be saying one thing and the Foreign Office another.”

The Foreign Office's official sanctions against Zimbabwe prohibit only the sale of arms. There are also travel bans and asset-freezing orders on senior members of the ruling Zanu (PF) party.

However, as supporters of Mr Mugabe unleashed violence before last Friday's rigged election, leading political figures had questioned whether Western companies should be in the country at all.

Lord Malloch-Brown said last week that Britain was considering whether to put pressure on companies doing business in Zimbabwe to withdraw as part of wider package of sanctions.

The Prime Minister then told Parliament: “We do not want to do further damage to the Zimbabwean people, but when businesses are helping the Mugabe regime, they should reconsider their positions.”

The Prime Minister's comments came after The Times revealed that Anglo American, one of the world's largest mining companies, was investing $400 million (£200 million) in Zimbabwe.

The company is building a platinum mine at Unki in central Zimbabwe, a move that has been condemned by the opposition Movement for Democratic Change (MDC).

The MDC believes that companies such as Anglo are helping to prop up the Mugabe regime through the transfer of foreign exchange and payments for mining licenses.

Some of the largest companies in Britain have a presence in Zimbabwe including Barclays bank, SABMiller, the brewer, and British American Tobacco, which makes Benson & Hedges cigarettes.

Those that have sought the Foreign Office's advice have been left with the impression that they should not leave Zimbabwe. Another businessman said: “We were told leaving could hurt the people of Zimbabwe, so we shouldn't. The politicians want to sound as though they are doing something without actually doing it.”

However, some companies, including Tesco, have already decided to quit Zimbabwe.

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