MSPs condemn lack of evidence behind SNP's £160m air tax cut

It said the “absence of supporting information” had the potential to “undermine scrutiny” of the policy, which is only supported by the SNP and Tories at Holyrood.

However the committee agreed to support the general principles of the Bill.

The committee also said evidence must be produced before MSPs were asked to set the tax rates and bands for flights departing from Scottish airports.

It recommended Finance Secretary Derek Mackay, who last month admitted he hadn’t commissioned any independent assessment of his own plan, should now order an economic impact analysis of it.

Air passenger duty (APD) is due to be devolved to Holyrood in April 2018.

Passengers currently pay between £13 or £26 on standard short-haul flights, and £73 or £146 for longer-haul flights, with private jet passengers paying up to £438 each.

The SNP manifesto promised to halve APD in the current parliament at a cost of up to £160m a year, then abolish it completely when resources allow.

Air line operators claim it will boost the number of services from Scottish airports and hence improve the economy.

But critics say there is little evidence for an economic uplift, and warn more flights will worsen pollution and undermine the SNP’s climate change targets.

Under the Bill, APD would be replaced by a new Scottish version called Air Departure Tax, administered by Revenue Scotland.

However the Bill is largely “enabling legislation”, with critical details such as tax rates omitted, so that ministers can set them at a later date using secondary legislation.

Mr Mackay wants the Bill passed before summer recess, with a view to specifying rates and bands in the autumn.

Bruce Crawford, the committee’s SNP convener, said MSPs recognised the legislation was of the enabling variety, rather than the finished product.

“Nevertheless, we are disappointed by the government’s lack of information on exemptions to the tax, and on the economic, social, financial and environmental impacts that will result from a 50 per cent reduction in ADT.

“The Committee considers it essential, therefore, that evidence of these impacts, to support the Government’s policy approach, must be made available in good time to allow for parliamentary scrutiny.”

Tory Murdo Fraser enthusiastically backed the policy. “Not only would it encourage more direct long-haul flights from Scotland, it would cut down the number of connecting flights which would help reduce our carbon footprint. It’s a proposal that offers the best value for money, and has the potential to deliver a real economic boost for Scotland.”

But Green MSP Patrick Harvie said it had “zero environmental credibility” and urged a rethink.

He said: “Cutting taxes for an already under-taxed industry in the hope that it will boost the economy is the worst kind of economic hocus pocus. This will just be an unfair tax giveaway to big business and wealthy frequent fliers, would harm public finances and would not address the real pressures most people face from the cost of day to day transport.

"I will continue to press for ministers to rethink their flawed plans."

Mr Mackay said he would “carefully consider all of the recommendations” in the report.

He said: “UK APD has been the most expensive tax of its kind in Europe and continues to act as a barrier to Scotland’s ability to secure new direct international services and maintain existing ones.

"Our plan to cut Air Departure Tax by 50 per cent by the end of the Parliament, and then abolish it when public finances permit, is a fundamental component to improving Scotland’s international connectivity and providing a real boost to our economy, which is especially important given the economic threat posed by Brexit.”