A Sunday Times investigation has established that the company, Halliburton, has been supplying Iran with oil drilling equipment through its companies based in Arbroath and Leatherhead.

The exports — estimated to be worth more than £30m a year — have continued despite sanctions introduced by the US government nine years ago barring Americans from trading or “facilitating” business with the Islamic state. The new findings will embarrass Cheney, President George W Bush’s running mate in next month’s elections. Cheney has described Iran as “one of the world’s most dangerous regimes”.

Although he resigned as Halliburton’s chief executive four years ago, Cheney has retained a substantial interest, owning an estimated $18m (£10m) in share options.

The company’s trade with Iran is already being investigated by the FBI for a federal grand jury inquiry ordered by the US Justice Department. It is believed that the firm’s managers in Britain could now also face questioning.

Halliburton, based in Houston, is the world’s largest oil-and-gas-services company and is also the biggest private contractor for US forces in Iraq.

Its trade with Iran was acknowledged in a confidential letter from Halliburton to one of its shareholders in October last year. It listed five subsidiaries involved: three in Britain, one in the Cayman Islands and another in Sweden.

The company said the contracts were not a breach because the subsidiaries were operating independently and no US citizens had carried out or “facilitated” the work.

However, inquiries by The Sunday Times have revealed that the company does appear to be flouting sanctions because some goods and equipment supplied to Iran were manufactured and designed in America.

The exports range from high specification oil drilling equipment, such as pumps, castings and “hole completion screens”, to domestic toiletries. They are imported into Britain from the United States by Halliburton Manufacturing and Services Limited (HMSL) in Arbroath. According to company insiders, the goods are then shipped on to Iran.

The company believes this is not a breach of the sanctions because it is supplying Britain with what it calls “stock items”, rather than equipment that was deliberately earmarked for Iran.

The Arbroath subsidiary is one of the area’s biggest employers, and Iran is a growing market for its engineering and manufacturing services.

The subsidiary’s trade with Iran soared after Cheney took over as chief executive of Halliburton in 1995. Last year it shipped more than $6m in drilling equipment and goods to Iran, but trade has grown substantially this year. The Sunday Times has learnt that the company has orders worth $2.6m for October alone.

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