An authentic Banksy image has been recovered from a derelict container on Dungeness beach in Kent after fears it could be destroyed by the landowners.

The elusive graffiti artist created the image, which depicts a bird with a head made of a petrol-pump nozzle, as an indictment of world pollution by oil companies.

The site’s owners, EDF Energy, had reportedly warned locals of their intention to clean up the beach, which would have involved destroying the container – and therefore the Banksy.

Fearing that time was of the essence, a local fisherman who owned the container sold it to John Brandler, a Banksy specialist and dealer, who has ensured its survival.

The picture, which measures about 8ft by 4ft (2.5 x 1.25 metres), was created in 2004. It was a sequel to a previous 2001 work – a bird perched on a branch – on the same derelict container, which had been stolen – cut from the side of the container – 12 days after its completion.

The second version had been preserved from the harsh sea air because a local fisherman had painted over it.

Brandler told the Guardian: “It was getting a lot of attention and bringing people on to the beach where the fishermen wanted to sell fish. Just after it was painted, someone threw a can of white household paint over it. The owner, because he was using the container as an office, just left it. Then EDF Energy wanted to tidy up the beach … He knew that if [they] sent a team of men … they would crush and destroy everything.”

He added: “EDF told the fishermen that they were going to tidy up the beach because it’s a nature reserve – which is rather ironic bearing in mind that this picture is all about the petro-chemical industry causing disasters … and birds being killed by petrol.”

Brandler removed the picture from the container with the help of independent construction recyclists Land Logical. The Dartford-based company used specialist equipment to salvage the container, recycling its metal and wood.

The restoration has cost him a “shedload of money”, he said, but the work is likely to be worth hundreds of thousands of pounds. He hopes that it will remain in the UK and is exhibiting it at the Brandler Galleries in Brentwood, Essex.

Last summer, Brandler helped save another Banksy painting that had appeared on a public toilet block in east London, only for it to disappear after it was vandalised, spray-jetted by the local council and then painted over.

Banksy, known for his stencil-based images, describes himself as a “quality vandal”, poking fun at authority figures through artworks in public places. Such is his popularity with the public that his Girl with Balloon – in which a child watches her heart-shaped balloon float away – was last year voted Britain’s best-loved work of art, ahead of masterpieces such as Constable’s painting The Hay Wain.

An EDF spokesman declined to comment.