The battle lines of the new parliament have been drawn following the devolution of major new powers to Holyrood.
With the arrival of the first of the Smith Commission powers, Scottish Liberal Democrat leader Willie Rennie demanded Nicola Sturgeon “look again” at her “£250million tax cut for airlines”.
His comments followed those of Finance Secretary Derek Mackay, who confirmed the SNP intend to press ahead with slashing Air Passenger Duty (APD), as well as plans to legislate on gender balance on the boards of public bodies.
The powers – over areas also including abortion, consumer advocacy and advice, equal opportunities, gaming machines, parking, speed limits, and policing of railways – are the first to be transferred to the Scottish Parliament from Westminster under the Scotland Act 2016.
Mr Rennie said: “Instead of supporting services, (the SNP’s) priority is cutting taxes for airlines.
“They claim this could cut prices for family holidays, but this will not replace the teaching assistants sacked as a result of their funding squeeze.
“(Yesterday) saw the first of the new powers that Lib Dems helped deliver through the Scotland Act 2016 arrive at Holyrood and there are more to come.
“Nicola Sturgeon needs to use the time she has before the tax powers are transferred to look again at her APD plans.”
Scottish Labour also do not want to cut APD, but the SNP argue it would be a major boost the economy.
Mr Mackay said: “We will look to attract more international flights to Scotland, boosting investment and jobs, by reforming Air Passenger Duty, which under the UK Government is one of the highest taxes of its kind in the world.”
The new Scottish APD powers are due to take effect in 2018, while control over income tax and enhanced borrowing powers will come to Holyrood in 2017.
Social security powers which are being devolved will also be transferred at a later date.
Scottish Secretary David Mundell hailed the arrival of the new responsibilities that will make “the Scottish Parliament one of the most powerful devolved administrations in the world”.
He added: “Crucially, these powers will be transferred while maintaining the benefits of a single labour market, pensions and the sharing of risk that comes with Scotland’s position in our United Kingdom.
“Scotland has two governments, each with different but complementary responsibilities.
“I have made clear that I want to work closely with the Scottish Government’s new ministerial team to work together in the national interest for the benefit of people in Scotland.”