The banksy mural in Jeffrey's Street was daubed with black paint last week. Picture: Polly Hancock

An urban art dealer has said vandalism to a famous Banksy mural in Camden may have quadrupled its value.

A tag by rivals Team Robbo on the Banksy mural. Picture: Polly Hancock

The image of a child blowing bubbles on the corner of Jeffrey’s Street and Camden Road was drilled into and stained with black paint last week.

It is the latest in a series of rival “taggings” and attacks on the artwork.

A graffiti turf war between rivals Banksy and Team Robbo has raged in Camden for more than a year.

But John Brandler, an urban art expert, said the work could be worth as much as £300,000 or £400,000 because of the history of taggings – as opposed to £100,000 without.

He said: “It’s an incredibly important piece. With the mural accumulating rival taggings, it carries marks of at least two artists, so becomes more valuable, especially since Robbo can’t paint anymore.”

Graffiti artist King Robbo has been in an induced coma since he sustained a head injury in April this year.

But some residents are fed up with the tagging war that the artwork attracts, despite being protected by a plastic screen and CCTV cameras.

A spokesman for Jeffrey’s Street Residents Association said: “I don’t see why I or anyone else has to look at it or why it should be protected.”

Bhupen Raja, owner of the house where the Banksy mural is painted, screened off the artwork hours after it appeared in June and has spoken of selling it.

But Pest Control, the official channel for selling Banksy art, has yet to approve it for sale.

Others want the artwork to stay. Mark Watts, a tenant of the house, said: “We have people here every day taking photos of it. It’s something unique about this street.”