Image copyright PA Image caption Michael Wheatley failed to return after leaving an open prison

A violent armed robber dubbed "the Skull Cracker" has gone missing after being allowed out of an open prison.

Michael Wheatley, 55, was given 13 life sentences at the Old Bailey in 2002 for a string of brutal raids on banks and building societies.

Kent Police said he failed to return to HMP Standford Hill open prison on the Isle of Sheppey.

Officers are now searching for Wheatley, with the public advised not to approach him.

Police said Wheatley, originally from Limehouse in east London, had links across south-east England.

He earned his nickname for using an imitation handgun as a blunt weapon to hit people - including a 73-year-old woman - during his robberies.

He raided 13 building societies and banks over 10 months in 2001 and 2002, starting just three weeks after he was released on parole from a 27-year sentence for other robberies.

The 2001-02 robberies took place over a wide area from Southampton in Hampshire to Royston in Hertfordshire.

'Completely ludicrous'

At the Old Bailey, in 2002, he received 13 life sentences for robbery and 13 concurrent five-year sentences for possessing an imitation firearm.

The judge said he must serve a minimum of eight years.

Conservative backbencher Philip Davies, MP for Shipley in West Yorkshire, said whoever allowed Wheatley out of prison was "a berk".

"It is completely ludicrous that a serving life-sentence prisoner is even in an open prison where they can simply walk out," he said.

"As far as I am concerned whoever allowed him to be in an open prison should be sacked."

'Hasn't been rehabilitated'

He said Wheatley's was not an isolated case.

"There are over 640 people serving life sentences in open prisons.

"He clearly hasn't been rehabilitated or else the police wouldn't be saying he was a dangerous person who shouldn't be approached."

Former prisons minister Crispin Blunt said it was "fantastically stupid" of Wheatley not to return to the prison.

A Prison Service spokesman said: "This is now a matter for the police and we are supporting them in their investigation.

Image copyright Met Police Image caption The Met Police issued a picture of Wheatley when he was wanted in 2002

"We are toughening up the release on temporary licence scheme so that prisoners will be subject to stricter risk assessments and tagged."

Prisons minister Jeremy Wright said the system had been too lax and was being changed.

"In future when prisoners are let out on temporary licence they will be tagged, more strictly risk assessed and tested in the community under strict conditions before being released," he said.

"There will be a full review of this case, which will look at the ROTL (Release on Temporary Licence) process."