BELFAST International Airport is the cheapest airport in the UK to park your car on-site for a week.

That's the findings in new research by Which? magazine which finds that Belfast International is one of the few big airports in the UK where it can be more cost-effective to park your car on-site than off.

Travellers who leave their car in the airport's long stay park for a week's holiday can expect to pay just £21 - if booked in advance on the internet.

Which? compared this with £24 in one of the off-site, independently-run car parks close by the airport.

The consumers' magazine assessed prices on and off-site for seven days parking at the UK's 11 biggest airports.

The prices quoted were for a booking from July 1 to 8 and all the off-site car parks surveyed were within 10 minutes transit of the airport itself.

Of the 11 airports assessed, Belfast International was by far the cheapest with Q-Park offering a space for just £3 per day, bookable in advance on the internet.

Birmingham airport came second in the survey. A week's parking there cost £43.40 - more than double that of Belfast International.

London Stansted's on-site parking was also cheaper than parking off-site, but here the price for the week was £50-40p - compared with £69 at an off-site park.

The only other airport where it was cheaper to park on-site was Luton, although it was only cheaper by 80p.

Q-Park generated something of a price war at Belfast International in May when it announced that prices at its on-site car parking were dropping to £3 per day over the internet.

Belfast International Airport officials are delighted with the findings of the Which? research.