SCOTS Tory leader Ruth Davidson has revealed plans to charge university students backdoor tuition fees of more than £6000 for a four-year degree course.

She confirmed plans to charge an endowment of "just over" £1500 for each year of study after students graduate.

She also revealed prescription charges would be reintroduced and rise to £8 within a few years, if her party wins the Holyrood election on May 5.

Details emerged during STV's live leaders' debate, held at Edinburgh's Assembly Rooms.

During a section of the two-hour debate in which the leaders cross-examined each other, Ms Davidson was challenged directly by SNP leader Nicola Sturgeon to spell out her plans.

The grilling followed heated exchanges between the leaders' of Holyrood's five parties on their tax plans, when Ms Davidson criticised her opponents for refusing to pass on George Osborne's generous tax cuts for higher earners.

University tuition fees were scrapped in Scotland by the last Labour-LibDem administration, which replaced them with a smaller graduate endowment.

Dubbed 'backdoor tuition fees,' the endowment was abolished when the SNP came to power in 2007.

Defending its return, Ms Davidson said scrapping charges had starved education of investment and led to the axing of more than 140,000 college places.

She said ending prescription charges had cost the NHS £60million a year, which she promised to re-invest in frontline services.

But, commenting after the debate, SNP business convener Derek Mackay said: "Rather than being a party of low taxes, we now know the Tories are simply the party of hidden taxes.

“It’s clear that Ruth Davidson is now on the run as the extent of her plans for hidden taxes have come to light."

The debate, the second of three televised showdowns in the run-up to the poll on May 5, included questions from the audience in addition to the cross-examinations.

Ms Davidson used her questions to attack Ms Sturgeon over her planned independence campaign later this summer, winning applause when she asked: "How is campaigning for independence respecting the result of the referendum?"

She also took a swipe at Kezia Dugdale, the Scottish Labour leader, who earlier this year said she allow her party's MSPs to campaign in favour of independence.

Ms Dugdale said she was "steadfastly opposed" to a second referendum.

Later in the debate, responding to a question from the audience about a possible second referendum, Ms Sturgeon said: "I think the next time we'll vote Yes.

"But I know we've got to get the arguments better than we did last time."

She said a future SNP government would call a second referendum if there was clear majority support for one.

Earlier in the debate, host Bernard Ponsonby had to step in repeatedly as the leaders clashed over their parties' tax plans.

Ms Sturgeon said the SNP's proposals for modest income tax cuts combined with  higher council tax bills for people living in bigger homes would raise £2billion.

But the plans were dismissed by Ms Dugdale and Mr Rennie, who have pledged to hike income tax.

Mr Rennie said: "The timidity of Nicola Sturgeon, I think, is letting Scotland down."

Setting out Labour's plan to raise basic and higher rate income tax by 1p and the additional rate by 5p, she said: "We can generate enough money to cancel the cuts."

She said a future Scottish Government would need to raise double the £2billion outlined by Ms Sturgeon to reverse cuts imposed by the Conservative Government at Westminster.

Turning to the SNP leader, she said: "She cannot feasibly say she is against austerity."

Ms Dugdale's comments were later seized on by the SNP, which said Labour's tax plans would fail to raise £4billion.