Budget airlines have appealed for the right to take up spare departure slots at Gatwick after national carriers including BA announced service cuts.

The national carriers have asked the European Commission to relax its "use it or lose it" rule, under which airlines which fail to fill a slot allocated to them at least 80 per cent of the time relinquish the right to hold it.

They argue that they cannot be expected to maintain normal services during the current period of low demand following the September 11 suicide hijackings in the US and should be allowed to retain the empty slots, thought to be worth up to £1 billion in the UK, until passenger numbers are restored.

But Ryanair chief executive Michael O'Leary today said any relaxation of the rules would effectively be an unfair state subsidy for struggling flagship airlines at the expense of no-frills operators like his own.

Mr O'Leary said: "It is absolute nonsense where, on the one hand, the EU is saying there will be no state aid to airlines but on the other hand says we are going to waive the normal rules. It's back-handed protection of monopoly high-fare carriers like BA that is outdated and shouldn't be allowed."

A spokesman for Gatwick said the allocation of departure slots was handled by non-profit body Airport Co-ordination.

A spokeswoman for Airport Co-ordination said some of BA's slots had been temporarily suspended.

But as long as the company continued to operate at least 80 per cent of its allocation at Gatwick, BA would not have to transfer any.

A decision from the European Commission is expected in ten days.

Karl-Heinz Neumeister, secretary-general of the Association of European Airlines, which represents major carriers like BA, said: "We are suffering and we are asking the commission to look favourably into the 'use it or lose it' rule."