The First Minister has branded Scottish Labour's plans to raise income tax a "con-trick" on the lowest-paid.

Nicola Sturgeon said the proposal for an immediate 1p increase in Scottish income tax rates was "out of touch" and "callous" during First Minister's Questions at Holyrood.

Labour says the plan, which includes a £100 rebate for the lowest-paid, would raise about £500 million every year, enough to avoid cuts to council budgets that will affect education and other local services.

Leader Kezia Dugdale challenged the First Minister to back the "fair and workable" proposal ahead of a vote to set the Scottish rate of income tax at the Scottish Parliament.

Ms Sturgeon replied: "Labour's policy is written on the back of a fag packet. The lack of detail, quite frankly, is embarrassing.

"But then it's a policy put forward by a party that knows it is a hundred million miles away from being a credible opposition, let alone a credible alternative government.

"It's a dishonest policy because Labour know it will hit the low-paid. That's why they're suggesting a rebate but haven't been able to answer a single question about how that works in practice.

"It's also a policy in its presentation from Labour that is out of touch and callous.

"Kezia Dugdale stands there as someone who like me, and like all of us, has a decent salary and yet she suggests that increasing the tax bill of the low-paid by 5% somehow doesn't matter.

"I say to Kezia Dugdale, tell that to someone who is struggling to make ends meet, tell that to someone who suffered years of pay freezes and is counting every penny."

She added: "Labour is perpetrating a con-trick on the lowest-paid workers in our society."

In response, Ms Dugdale said there was "very clear evidence" from independent experts that her party's proposals are "fair and workable".

She said: "That is why council leader after council leader has backed it, that is why union leader after union leader has said it is fair.

"That is the truth that the First Minister cannot escape.

"The First Minister and I have something in common here. We both oppose George Osborne's austerity and we both want the best for our country.

"Where we part is that Labour has a fair plan that will ask some of us to pay a bit more and the wealthiest few to pay a lot more.

"In so doing, we can stop these cuts, cuts that would damage our economy and stop young people from achieving their potential.

"Faced with the choice between using the powers of this parliament to invest or cutting schools, why does the First Minister choose cuts?"

MSPs were rebuked by Presiding Officer Tricia Marwick for their behaviour during the session after a call of "liar" was shouted across the chamber as Ms Sturgeon was speaking.

Warning she would take action unless an apology was forthcoming, Ms Marwick said: "I already warned the chamber about heckling the First Minister or anybody else who's speaking.

"There was a remark that came across the chamber, I didn't quite hear it but I think from the reaction in the chamber there was the use of a word which was clearly unparliamentary."

Ms Sturgeon said: "We know how desperate Labour are by the volume of the insults they like to sling."

Earlier, Ms Dugdale brandished what she said were 186 pages of cuts being proposed by Perth and Kinross Council as a result of the controversial local government settlement reluctantly agreed by all of Scotland's 32 local authorities.

She said: "That is the SNP council in John Swinney's backyard.

"Cuts to childcare, cuts to help for those with additional support needs, cuts to early-years teachers, cuts to maths and English teachers.

"Page after page contains a warning of SNP cuts that will harm our children's future. That's the reality from one of the First Minister's own councils.

"When will she stop pretending that her budget won't harm our children's future?"

The Labour leader added the council was cutting its entire budget for supply teachers, quoting from the document: "It states 'classes may have to be sent home and possibly schools closed'.

"That is the scale of the cuts she is forcing on schools."

Ms Sturgeon said the 2% reduction to councils' total revenue spending was offset by a £250 million investment in social care.

The settlement allowed the Government to protect teacher numbers, shield households from council tax rises, expand social care and ensure social care workers are paid the living wage, she said.

"That is the reality of the position of this government, of course, in the context of a budget cut from Westminster imposed on this government.

"A budget cut that Labour when they campaigned so vigorously with the Conservatives were quite happy to see imposed on this Parliament."

Liberal Democrat leader Willie Rennie said SNP-run Aberdeenshire Council were also considering education cuts as they decide their budget.

About £3 million worth of cuts are on the table, he said.

Mr Rennie said Ms Sturgeon was making the "same old excuses" over stopping them.

"I would have sympathy for the First Minister if she did not have the power to do something about it," he said.

"But she does, the buck stops in that seat over there.

"This afternoon this Parliament votes on the income tax resolution. One penny gives £475 million for education, for Scotland's children.

"It's the power to stop the cuts. She has the power, why won't she use it? Is it pride, is it her Finance Secretary, or does she simply not care any more?"

Ms Sturgeon responded: "It is no surprise to me that the leader of a party that spent five years in coalition with the Conservatives doesn't care about people on low wages.

"I do care about people on low wages, struggling to make ends meet.

"Willie Rennie's policy of putting a penny on the basic rate of income tax - he is not even pretending that he is going to try and compensate low-income workers the way Labour is.

"His policy would have everybody above £11,000 a year paying more in tax. I think that's transferring Tory austerity to the shoulders of the low-paid."

The Scottish Parliament's Official Report of First Minister's Questions later named Labour's Neil Findlay as the MSP responsible for the "liar" shout.