Around 72,000 tonnes of crude oil were spilled into the estuary.

The claim was submitted in February 2002, just before the final deadline, but has only now been confirmed by Texaco.

It is not the only multimillion pound action that the port authority is facing over the disaster.

The International Oil Pollution Compensation Fund is seeking £34m for money it paid out to the victims of the disaster, together with any further compensation it may have to pay in future.

More than 200km of the west Wales coastline was affected when the Sea Empress ran aground in February 1996, spilling 72,000 tonnes of crude oil into the estuary.

The spill caused a major environmental disaster

The 147,000-tonne Norwegian-owned tanker struck rocks at the mouth of the estuary near St Ann's Head - it was the third-largest tanker spill in UK waters.

The port authority's general manager Ted Sangster has said its lawyers thought they had a good defence against Texaco's claim.

But, he added, there was a "sense of embarrassment" that the authority's major customer was making a claim against it.

In a statement, Texaco said that it has made its claim to protect its legal position in the aftermath of the disaster.

It confirmed it had issued a claim form against the Milford Haven Port Authority and Milford Haven Pilotage Limited.

"The official Marine Accident Investigation Branch (MAIB) inquiry into the incident found the cause of the grounding to have been contributed to by pilot error, the statement read.

"The claim form was issued to protect Texaco's legal position.

"There is no requirement to announce publicly the commencement of proceedings, nor is it common industry practice to do so."

The statement added that Texaco could not discuss the details of claim, as it could prejudice any legal proceedings that might take place.