Police have launched an investigation after yobs spray-painted a penis onto the empty plinth on Folkestone's Banksy.

But luckily the damage was not permanent as Shepway District Council had already taken the precaution of covering the artwork, worth an estimated £300,000, with sealed perspex which has now been fully cleaned.

The offending image was discovered on the painting in Payers Park last night, and police are investigating it as criminal damage.

The painting, depicting a woman looking at the plinth, appeared in the town centre spot last month.

The council have again moved quickly to protect the artwork which it says has been considered as "a valuable cultural addition" to the town. Shortly after the work was revealed by Banksy as genuine, council staff protected the piece.

This morning, the crude addition was scraped off the perspex using specialist removal treatment by a council officer who had spotted the offensive edit at 8.30am.

Andy Blaszkowicz, grounds maintenance manager, said: “The officer saw the crude image from where he was working in Payers Park.

"He immediately returned to the office to collect the equipment he needed to clean it off. We always endeavour to act quickly when made aware of images of such an offensive nature.”

'Art Buff' quickly became one of the biggest attractions in Folkestone, which is currently staging its Triennial arts festival.

Initially, the piece had been guarded by security personnel and two people have again been spotted in place at the location today.

A police spokesman said: "Kent Police was called at 8pm on Sunday 12 October to a report of criminal damage in Rendezvous Street, Folkestone.

"It was reported artwork on a wall had been painted on. Officers attended the scene and enquiries are ongoing."

The council added it is working with the police to find the culprits during the investigation.

Hundreds of people have visited it while thousands more posted on social media to celebrate the piece after the anonymous artist revealed on his website it is an original.

It is not the first time a Banksy has been targeted by vandals.

Earlier this year, another work daubed on a Brighton pub hit the headlines after fetching £345,000 at auction in Miami.

The Kissing Coppers, which shows two policemen sharing a passionate moment, was splashed onto the Prince Albert pub in the city.

Following vandalism in 2006 when black paint was smeared over the original the landlord of the pub cleaned up the offending paint and gave the Banksy a restoration, before having it removed by specialist workers.

Two people pleaded guilty to causing criminal damage and the piece was sold controversially as an original Banksy in February.

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