Leaving the UK's airport capacity at current levels is an "unrealistic option", Alistair Darling has told MPs.

Warning that increased capacity is essential, the transport secretary said leisure-based travel would continue to increase as people become richer.

"The traditional model in this country where people go away for one holiday a year is changing. People go away for weekend breaks," he said. "In the last year or so half the population flew at least once."

Darling said the government's aviation consultation, which closed on Monday, was an attempt to gauge the likely growth in demand for air transport.

But giving evidence to the Commons environmental audit committee, he was cool on suggestions that the tax system should be used to limit the increase in air travel.

"There are a range of options available to us. The over-riding objective must be to reduce the harmful emissions which are caused by air travel," he said.

"The government has not reached a conclusion about the best way forward."

Any attempt to change the tax regime on airlines to make the "polluter pay" would have to be agreed at an international level, the minister told MPs.

"The government's objective is to cut down emissions," said Darling.

"But I have doubts about a policy in which you explicitly drive people off aeroplanes and you say to people that 'you can't travel'."

Darling denied, however, that the government was still adopting a "predict and provide approach" to air travel.

"The idea that somehow we are just going to say let's have a whole lot of new runways is just nonsense," he said. "It's not predict and provide at all."