Murray has upset the authorities in Tashkent

Craig Murray's return to the UK comes less than a week after he went back to Tashkent following a two-month absence.

His earlier return to Britain in September prompted speculation he was removed because of a high profile attack on the state's human rights.

But the Foreign Office are insisting he is again absent for medical treatment.

Vocal critic

However, officials would not specify the nature of his medical problem.

"We won't give out any more details about a member of staff's personal circumstances," the department said.

They also did not say who would act in his place in the meantime.

Mr Murray has been a vocal critic of Uzbekistan's human rights record.

In his first speech there he said: "Uzbekistan is not a functioning democracy, nor does it appear to be moving in the direction of democracy".

Uzbekistan is not a functioning democracy Ambassador Craig Murray

Demonstrators had rallied outside the embassy in Tashkent in support of the ambassador when he left in September.

They said he was under pressure to resign for being overly critical of the United States' key ally in formerly Soviet Central Asia.

Embassy spokesman Leonid Kudryavtsev insisted Mr Murray was expected to come back when his condition improves.

But Uzbek officials earlier said he was unlikely to return.

Murray has upset the authorities in Tashkent

With more than 6,000 political prisoners in jails, where dozens of people have reportedly died from torture, Uzbekistan has long been criticised for its human rights record.

But its border with Afghanistan and willingness to let hundreds of US troops be based on its soil has made it a key American ally in the US-led war against terrorism.