Police officers have been advised not to wear their uniforms on the way to and from work amid concerns that Islamic extremists are plotting to target them on the streets, it has been reported.

It comes as MI5 fears that extremists are planning an attack on an officer similar to that of Fusilier Lee Rigby, killed last year by two fanatics as he walked near his Woolwich barracks.

Now seniors at Scotland Yard have warned officers to keep a low profile outside of work, issuing advice on what to wear when travelling to work and urging them to keep social media clean of all personal information.

Police officers have been advised not to wear their uniforms on the way to and from work amid concerns that Islamic extremists are plotting to target them on the streets. Michael Adebolajo (left) and Michael Adebowale (right) were sentenced to life imprisonment for the murder of Lee Rigby

It comes after police raised their internal threat level last month from 'moderate' to 'substantial' last month

A source told the Mirror: 'A raised threat level means officers have to be extra vigilant in everything they do.

'It means not travelling to work in full uniform and standing out unnecessarily out of work.

'Officers are also being warned about putting sensitive information about their personal lives on social networking sites such as Facebook, Twitter and Instagram.'

Fusilier Lee Rigby was killed in Woolwich after crossing the road near his barracks

Military commanders issued similar advice following the murder of Drummer Lee-Rigby in Woolwich in May last year.

They later rescinded the advice that 'uniforms should be concealed while in a public place, particularly when travelling alone or from home to unit.'

Drummer Rigby was not wearing his uniform when he was attacked, but a Help for Heroes hooded jumper.

The Mirror reports that GCHQ has picked up talk of targeting a British police officer, and now MI5 are looking at intelligence that social media profiles of police officers are being monitored by jihadists.

In October a gang was arrested accused of scouting Shepherd’s Bush police station and White City Territorial Army barracks in a ‘hostile reconnaissance’ mission using Google Street View.

They were said to have kept Instagram images of two Scotland Yard police officers and two community support officers. The group is also charged with amassing jihadist material, including videos of beheadings.

Security expert Neil Doyle told the paper: 'It makes perfect sense that terrorists would be using social media to scout for targets.

'The risk is that officers and PCSOs giving away precise details of their movements and routines may leave them open to being abducted by fanatics.'

On Saturday it was revealed that internet service providers did not raise the alarm about extreme messages posted by one of the killers of Fusilier Lee Rigby in the six months before his death.

The companies - who have come under intense pressure to do more to help police and the security services - failed to inform authorities about material posted by Michael Adebolajo before the attack he carried out with Michael Adebowale.

It meant MI5 missed internet messages that could have alerted them to the threat posed by the murderers.

A long-awaited report by Parliament’s intelligence watchdog is expected to say Adebolajo was posting extremist material on social media sites in the months leading up to the attack.

The messages would have been sufficiently serious to justify the security services – who had had Adebolajo on their radar for eight years – putting him under more detailed surveillance.

But officers found out about them only after the sickening murder of the 25-year-old soldier outside Woolwich Barracks in May last year.