Scotland should use its new powers to cut taxes and cap benefits, Conservative leader Ruth Davidson has said.

The Tories will launch a "low tax commission" next year to examine how powers devolved by the Smith Commission could turn Scotland into "a dynamic, low-tax nation".

She has also proposed a cap on welfare to ensure no-one can claim benefits more than the average family wage.

Deputy First Minister John Swinney has also called for the devolution of air passenger duty (APD) to be fast-tracked, suggesting he intends to follow through with pre-referendum pledge to half the duty with a view to abolishing it by 2020.

He called for all other powers in the Smith Commission that do not require primary legislation to be fast-tracked.

Ms Davidson said: "I want to reduce the taxes that we will be responsible for. Early next year, the Scottish Conservatives will launch our low tax commission.

"This will examine how we can better use the basket of taxes which we will soon have control over and advise us how best we go forward as a dynamic, low-tax nation.

"Secondly, we will support all moves to grow the tax base. The Gers (Government Expenditure and Revenue Scotland) figures show, that per head of population, our income tax receipts in Scotland are lower than the UK as a whole.

"Get those receipts up to UK levels, however, and nearly two billion pounds more per year would flow into the Scottish Government's coffers.

"That creates a real incentive for this government to do so.

"With half of all VAT assigned here too, there is also an incentive to grow retail sales to support Scottish businesses who make and sell things."

She added: "I support reform of our welfare system that gives help and encouragement to people to get back to work and which cuts the country's benefits bill. The SNP oppose that reform.

"I back a cap on the amount any one family can claim in welfare. The SNP says they want to lift the cap.

"I believe you shouldn't be able to claim more in benefits than the average family earns through work. The SNP doesn't agree."

Conservative finance spokesman Gavin Brown urged the SNP to explain what it would do with its new tax powers if they were fast-tracked, particularly on APD.

Mr Swinney said: "The White Paper set out that we would half APD with a view to, over time before 2020, move to abolish it.

"Ruth Davidson is saying 'let's devolve the power for 16 and 17-year-olds (to vote) and let's do nothing else'.

"But let's look at other provisions like the work programme.

"We all sat in the Smith Commission and signed up to words in the document which said: 'We will devolve the work programme at the end of the current contract'.

"While we're doing that we find out that the UK Government is negotiating with the work programme contractors to extend the contract."

Liberal Democrat MSP Tavish Scott called on the Scottish Government to heed Lord Smith's recommendation for devolution to be extended further by the transfer of powers from Holyrood to local communities.

He said: "This government has ruthlessly centralised decisions to create the trappings of state in Edinburgh.

"Each and every part of Scotland has lost out - the judgements of local people have been over-ridden by an ever-mightier central government."

Mr Scott argued that local authorities and communities had been "systematically stripped" of control over their funding and taxes, as well as local services including police, courts, hospitals, colleges and the fire service.

He said: "Liberal Democrats want a different approach. We believe that local people can be trusted with more powers to shape their local areas.

"Local people are best-placed to make decisions about the services which affect them, day in and day out.

"The SNP promised time and time again as they centralised that services would be flexible and responsive to local needs. People know that this has not been the case.

"I hear much about listening to those who made their case to the Smith Commission. The Scottish Government must heed these calls. They must stop the power grab."

He called for the responsibility for the management of the Crown Estate's economic assets and revenue to be devolved to local authority areas such as Shetland and Orkney, as well as for greater independent scrutiny of the Scottish Government's finances.

Labour MSP Drew Smith said: "Powers should be exercised in the interests of people and at the level where the people's voice is most easily heard.

"Pulling and sharing risk and resource where it's in Scotland's interests to work with our closest neighbours, taking responsibility for ourselves where we can make a difference and devolving power away from the centre so that local government becomes more than just local administration.

"We would use the new powers to ensure that those with most pay a fair rate of tax, that's why we support the reinstatement of the 50p tax rate.

"We would reform the work programme so that it responds to the real needs of the regional economies within Scotland, and having placed the issue of double devolution at the heart of the debate, we will stand by our commitment not just to Scotland's cities but also to Scotland's islands."

He added: "To 2016 and beyond the challenge is not constitutional, it becomes political, and the greatest test of political will is not collecting tools for your toolbox, it's the good to which you put the tools that you have to work."