There was confusion this morning over which authority is ultimately responsible for allowing a man wanted for the murder of policewoman to flee the country after he disguised himself as a Muslim woman.

Mustaf Jama, a prime suspect in the fatal shooting of PC Sharon Beshenivsky, assumed his sister’s identity — wearing the niqab and using her passport — to evade supposedly stringent checks at Heathrow, according to police sources.

But today the Home Office, BAA and the Department of Transport all denied that the fault lay with them.

At the time of his departure, Jama was Britain’s most wanted man, while Heathrow was on a heightened state of alert after the 7/7 terrorist atrocities in London five months previously. The Times has learnt that British immigration officers rarely carry out a visual check to match a passport photograph with a departing female passenger’s veiled face.

Liam Byrne, the Home Office Minister, refused to comment on what he said was "pure speculation" about Jama.

"It is standard practice for immigration officers to ask people to lift the veil - more than that, if immigration officers have got suspicions they fingerprint people and check them against our databases," he told BBC Radio 4’s The World at One.

"That’s exactly how we caught 750 offenders in one month alone - November - at Heathrow.

"We don’t have exit controls around the clock, around all of our borders; what we do make sure we do is respond immediately to police requests for those exit controls."

Mr Byrne said it would take around four years to ensure "near enough 100 per cent" border controls.

A spokeswoman from the Home Office said it was important to differentiate between the role of immigration and the role of security staff.

When someone leaves the country, she said, checks are carried out by airline transport security, not, routinely, by immigration, who check people entering the country.

"Exit controls are carried out on people leaving the UK alongside security checks carried out by airlines and airport operations," she said.

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