SCOTTISH Labour’s flagship election policy was in disarray yesterday, after the party repeatedly refused to explain how it would avoid penalising the low-paid.

Labour leader Kezia Dugdale last week proposed adding 1p to all three income tax bands - 20p, 40p and 45p - next year in order to raise almost £500m for education.

Under the plan, everyone earning over the £11,000 tax threshold would face higher bills, but those earning between £11,000 and £20,000 would be fully compensated by a £100 “rebate”.

Labour said the rebate would be delivered by councils, but did not explain how.

The SNP yesterday pointed out that if, as suspected, the rebate is linked to benefits, there is a massive potential problem - not everyone entitled to benefits actually claims them.

In the case of working tax credit and pension credit, around a third of people don't claim.

With an estimated 1m people in Scotland earning between £11,000 and £20,000, the SNP said that implied around 350,000 people would miss out on Labour’s rebate.

MSP Mark MacDonald said: “Since announcing their plans for a tax hike on low-earners, Labour have claimed that their proposed rebate would protect the poorest workers– but the fact is that Labour have no way of telling us how this scheme would work, or how they could guarantee that the rebate gets to those who need it most.

“The reality is Labour cannot guarantee that a single person would claim or receive this £100, but if Labour ever got into power everyone would have to pay more taxes.”

Asked about the SNP claims and how Labour would identify those entitled to the rebate, a Labour Party spokesman said: “The unions say Scottish Labour's plan is fair and councils say it is workable. This is desperate stuff from the SNP who this week endorsed George Osborne's tax plans and voted for hundred of millions of pounds of cuts to schools and local services."

Pressed for more detail, the spokesman refused to explain the mechanism and said he was watching the Scotland-England Six Nations rugby match, adding: “That’s all you’re getting.”

Dugdale was also forced to defend her candidate line-up yesterday after criticism about the number of Holyrood and Westminster re-treads on offer.

Despite saying she wanted fresh talent in her team, only eight of the 32 top-ranked list candidates are new to Holyrood or Westminster.

With the SNP predicted to win almost every constituency, the list rankings are now vital to Labour, as they will yield most if not all of the party’s MSPs.

Among those in the running are ex-MSP Pauline McNeill, who lost Glasgow Kelvin to the SNP in 2011, and ex-MPs Anas Sarwar and Thomas Docherty, who lost their seats last year.

However some current Labour MSPs do face the chop in May because of low rankings, including Paul Martin, Patricia Ferguson, Hanzala Malik and Anne McTaggart in Glasgow, and father and daughter Michael and Siobhan McMahon in Central Scotland.

Speaking alongside candidates in Edinburgh, Dugdale said she was “proud” of those chosen by party members.

"What you've got is a mix of experience and new blood.

"We've got an employment lawyer, we've got a teacher, we've got a small businessman, a very prominent trade unionist, these are strong candidates, these are strong campaigners."

Dugdale’s deputy, Alex Rowley, was confirmed as campaign manager, mirroring the role performed by Deputy First Minister John Swinney for the SNP.

The Scottish Greens will tomorrow unveil a campaign logo based on the Saltire at their election launch, as they try to win list votes from SNP and independence supporters.

A new slogan, ‘A better Scotland needs a bolder parliament', is also designed to present the Greens as more radical than the SNP has been in government.

Brand adviser Ian Dommett, who helped craft the SNP’s winning “It’s time” campaign in 2007 and is now working for the Greens, said: “The more Scottish Green MSPs in Holyrood the bolder the agenda, the more far-reaching the effects, the brighter the future. This is a message that will resonate with those looking for a change of pace, of ambition and political tone.”

Meanwhile the SNP will repeat its approach to the general election by foregrounding Nicola Sturgeon.

The party has registered four new names for possible use on ballot papers, three featuring Sturgeon: “Scottish National Party (Leader – Nicola Sturgeon)”, “Nicola Sturgeon for First Minister” and “Nicola for First Minister”.

It was reported yesterday that SNP members will be denied a say on the timing of a second referendum when their pre-election conference meets in Glasgow next month.

A leaked draft agenda contained no mention of the subject, confirming the Sunday Herald’s reports that there will be no firm commitment to Indyref2 by 2021 in the manifesto.

Former SNP deputy leader Jim Sillars said Sturgeon was playing “dodge the referendum”.