THE Liberal Democrats have defended their call for a new tax on domestic flights, which Westcountry airlines warn could wipe out key routes.

Norman Baker, the party's transport spokesman, accused Exeter-based Flybe of "squealing" at the prospect of a £20 surcharge and rejected claims the "unworkable plans ignore the world outside the M25".

The Lib-Dems remain committed to "comprehensive improvements to public transport" in the region, he said.

Last week, Lib-Dem leader Nick Clegg unveiled what he described as a radical package of tax reforms which would target the wealthiest members of society.

Combined with new green taxes, anti-avoidance measures and cutting relief for high-earners, the Lib-Dems want to lift four million people out of income tax altogether.

He said the levy on all domestic flights on routes which could be covered by train in under six hours would, on average, add £20 to a plane ticket.

Flybe chief commercial officer Mike Rutter said the "calamitous and naïve" proposals posed a "real threat" to the region's economic recovery.

"I'm not a politician, but the idea of slapping an extra £20 on regional aviation seems to be an attack on their own constituents who choose to fly in order to do business or take a well-deserved break," said Mr Rutter.

"A curious case of political self-flagellation, indeed."

But last night, Mr Baker insisted the plan needed to be put "in context".

"The growing threat of climate change requires us to give people incentives to use less-polluting modes of transport, yet the cost of flying – one of the most polluting ways to travel – has decreased by more than any other mode of transport since 1997."

He has obtained figures which show an average UK one-way air fare cost £94 in 2008, down from £204 in 1997.

"Our proposed surcharge represents only a fraction of the reduction since 1997. The squealing by individual airlines needs to be seen in this context."

He said that a "small surcharge" on non-lifeline domestic flights would create an incentive for people to use greener modes of transport, while also raising revenue.

Rejecting claims to have ignored life outside the M25, Mr Baker said the Lib-Dems "want to see a comprehensive high-speed rail network across the country, eventually to the South West".

This would reduce the journey times involved in travelling by train, and would provide a viable and environmentally friendly alternative to short-haul domestic flights.

He said the party had also pledged to electrify "virtually the entire rail network by 2050" and wanted to "reopen for passenger traffic the lines between Exeter and Okehampton, and between Plymouth and Tavistock".

He was also promoting "the redoubling of lines which should never have been singled, such as those between Exeter and Salisbury, and between Swindon and Kemble".