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Bacon's triptych Two Figures Lying on a Bed with Attendants is seen one of the artist's major works.

It was bought by the last Shah of Iran and was destined to be exhibited in his wife's museum in the city.

But the 1979 Iranian revolution resulted in the painting being put into storage as it was deemed indecent.

A spokeswoman for the Tate said: "We have requested the loan of the work. But we have yet to receive confirmation.

"The museum director is very keen to show the work. It is a major work by Francis Bacon and it has not been shown for more than two decades.

"It is such a key painting and it should be shown at the home of British art."

The request is going through official channels and is expected to take a month.

Two years ago Tate Britain's director Stephen Deuchar visited the modern art museum in Tehran and returned last month for talks with its director, Dr Sami Azar.

He was shown the Bacon painting during the visit.

"I thought it would be rather great to see it in this country in the context of some other Bacons," he told the Independent newspaper.