UK laws make it too easy for shipping companies to pollute the seas and get away without paying their dues, says an influential MPs' watchdog.

As well as urging tougher measures against polluters, the Commons public accounts committee condemns inconsistencies between rules in different parts of UK shores.

In some parts of the coast polluters have much more protection from prosecution than in others. Edward Leigh Watchdog chairman

The UK has not suffered a major oil or chemical spill since the Sea Empress disaster in 1996 and the committee says its record has got much better in recent years.

But the MPs warn a major pollution incident could happen at any time and that there also should be contingency plans for terrorist threats at sea.

The danger of oil spills has recently been in the spotlight again with the sinking of the Prestige tanker off Spain.

And only last weekend the World Wide Fund for Nature (WWF) marked the tenth anniversary of the Braer sinking off the Shetland Isles to warn that vulnerable areas of Britain's coastline still needed better legal protection.

In the UK, the Maritime and Coastguard Agency (MCA) is responsible for minimising pollution and enforcing international rules.

As the new report was published on Thursday, public accounts committee chairman Edward Leigh said: "The system is not tough enough on those who pollute our seas."

Too many polluters were able to avoid paying for the problems they caused by setting up "one ship companies", said Mr Leigh.

The impact of oil spills can be devastating

That means that if a ship is wrecked or scrapped after a pollution incident, there may be no other assets against which the MCA can claim compensation.

Conservative MP Mr Leigh continued: "What's worse is that in some parts of the coast polluters have much more protection from prosecution than in others.

"For example, it is paradoxical and perverse that the owners of a ship causing pollution close to Southampton or Portsmouth would be very difficult to prosecute.

"But if the incident took place further out in the English Channel prosecution would be much easier."

That problem, says the committee, is caused by the limits on the MCA's ability to prosecute offences in the UK's main estuaries.

The Cabinet Office is currently looking at contingency measures for any possible sea-based terrorist attacks on the UK.

The MPs say the problems posed by a terrorist attack at sea may be very different from those faced in the wake of an accidental spillage.

The government and the MCA must "put in place appropriate prevention and response plans to deal with terrorist threats involving vessels carrying potential problems", they say.

Tracking polluters

The Prestige incident brought new concerns about the risks posed by using single-hulled oil tankers.

The committee urges the MCA to particularly target such vessels with its port inspections.

New technology, such as satellite surveillance and better oil spill sampling, can also be used to trace offenders.

The report says the MCA believes it can handle more than one spillage incident at once.

But the MPs urge the agency to map out the limits of their capabilities and work out what outside help they could call upon if necessary.

Research for the government suggests a 100,000 oil tonne spill is probable in UK waters every 17 years.

A 4,000-tonne spill is likely every other year.