OIL washed up on a stretch of East Anglian coastline could have a devastating impact on wildlife and the future of tourism and fishing industries, it has been warned.

OIL washed up on a stretch of East Anglian coastline could have a devastating impact on wildlife and the future of tourism and fishing industries, it has been warned.

Tar lumps of heavy oil were found washed up along a 12-mile section of beaches from Dovercourt Bay to Martello Bay at Jaywick yesterday in Essex, although the explanation of its source has yet to be identified.

There are fears the emulsified oil, up to 1ft across, could be from a slick discovered at Felixstowe Oil Jetty last Thursday, although the stranded vessel, the Tricolour, in the English Channel, has not been ruled out as the source.

A slick of oil, which is lighter in density, has also hit a three-mile stretch of coast from Harwich downwards and has left sea birds coated.

Dispersed oil has also entered the world famous backwaters at Walton on the Naze, home to a wide variety of sea birds, which the RSPB has warned could lead to their deaths.

A clean up operation has started although Tendring District Council said its workers were being stretched by the workload.

Lawrie Payne, of Tendring District Council said he feared the extent of the damage.

He said: "The spillage is serious because of its impact on the wildlife – the rescue centres will be swamped by oil covered birds which will be a disaster.

"The effects on such a long and varied coastline cannot be under estimated – there are the breeding sea birds which are coming in at this time of year – it is going to be quite devastating.

He added he feared for the long-term impact to the local fishing industry and damage the pollution could cause to the Blue Flag status of the beach at Dovercourt.

The Maritime and Coastguard Agency (MCA) is responsible for responding to pollution from shipping and offshore installations.

The agency gave the spill a tier one status, classified as a small operational one, which would require local resources for the clean up operation.

It sent up a spotter plane yesterday to assess the extent of the area affected and has also taken samples of the oil for testing.

A spokesman said the results could be back by today, which should identify the source.

"It would appear most of the oil which has been reported is breaking up and washing ashore," he said.

Tendring District Council said it thought the heavy oil was different to the slick from Felixstowe.

A spokesman said: "We have been finding heavy oil like tar balls and it is different to the spill from the split pipe at Felixstowe - this is a second kind of a spill and very defiantly a different kind of oil.

"We have had a team out there today who have been cleaning up the tar balls along a 20km stretch of beach, although we can only be in one or two places at once.

"We don't know what the exact impact will be, but we will not be closing the beach – however, if you are thinking of walking the dog you should be aware of the oil which is around.

He added the clean up team would be returning once the tide had gone back out again, although it was hoped the smaller balls would break down naturally.

The council also said the problem would not affect the blue flag status which is held by Dovercourt beach.

Leon Woodrow , wildlife warden for Tendring council, said the oil which had gone into the backwaters at Walton on the Naze was a diesel "film" which came in with the tide and then went back out again.

"The oil which came in yesterday was from the initial leak at Felixstowe and had been treated with dispersant.

"If the heavier oil gets on to the mud here the best thing is to leave it because the dispersants all do more harm and it is best left alone to break down naturally.

The RSPB has warned any damage to the backwaters could be hidden from view because of the nature of the area.

There is a network of muddy creeks, islands and salt marshes which are hard to gain access to.

Chris Durdin, of the RSPB East Anglian office, said: "It is a very complicated area of salt water marshes with wading birds but the damage will depend on just how far in the oil gets.

"The oil would be likely to kill birds, however it is not practical to get in there and it may have to be a case of waiting to see what damage has been caused.

Essex County Council's emergency planning department was also brought in to deal with the problem.

A spokeswoman said: "We really can't tell how serious it is at the moment although we are just acting in a supporting role at the moment."

Harwich MP Ivan Henderson said he was talking to the various agencies dealing with the oil slick and would keep in contact with them as they continued their work.

"Once the situation has been brought under control, then there will be a need to look at what happened in order to try and learn lessons from it," he added.