The SNP’s income tax plans have been criticised by former finance secretary Kate Forbes  as “ultimately counterproductive”, in a coded rebuke to Humza Yousaf.

Ms Forbes said continually increasing taxes also “reduced public revenue”, as it created ever greater incentives for people to avoid paying them.

The Scottish Tories urged the Skye MSP to “take a stand” and vote against the Scottish Government’s Budget Bill for 2024/25.

READ MORE: SNP ministers face FoI investigation after deletion of Covid WhatsApps

The dissent, reported in the Scottish Mail on Sunday, follows finance secretary Shona Robison raising income tax for all Scots earning over £28,000 in her budget in December.

Ms Robison, who is Mr Yousaf’s deputy First Minister, also introduced a new income tax band aimed at high earners, giving Scotland six bands to England’s three.

South of the border, wages above the £12,570 personal allowance are taxed at 20% up to £50,270, then at 40% up to £125,140 and then at 45% above that.

However if, as expected, MSPs pass the 2024/25 budget at Holyrood, Scots will be taxed at 19% between the allowance and £14,876, then at 20% up to £26,561, then 21% up to £43,662, then 42% up to £75,000, then 45% up to £125,140 and finally at 48% above that.

It means someone earning £50,000 in Scotland will pay around £1,500 more than their equivalent in England and Wales, and around £3,300 more if they earn £100,000.

Holyrood’s independent budget watchdog, the Scottish Fiscal Commission, calculated most of the most raised in theory from the top-end hikes would be lost to avoidance.

While the new “advanced” rate of 45% should in theory raise £147m, the yield drops by 59% to £74m once behavioural change, such as cutting hours to avoid it, is factored in.

Increasing the top-end additional rate from 47 to 48% should also raise an extra £53m, but almost all of this is lost to behavioural change, with just £8m being collected.

Writing in a Highland newsletter, Ms Forbes, who came a close second to Mr Yousaf in the SNP leadership contest last year, questioned the government’s approach.

She wrote: “Continually increasing taxes is ultimately ­counter-productive over the long term, even if you agree with it i­deologically, because it ultimately reduces public revenue. 

“The forecasts for what the Scottish Government will raise through its latest changes to the top tax bands is just over £80million. That isn’t to be sniffed at. 

“But the forecasts also suggest that they’ll lose £118m that they could have raised because of behavioural change – ­people leaving or reducing their hours or treating their income differently. 

“That illustrates that we need to invest in people, in job creation, and in better wages. That way the tax take will increase.” 

The Herald:

Rather than taxing existing earners more, she said the best plan was to increase the number of people paying tax in the first place, thereby broadening the tax base.

“I’m constantly going on about the tax base. What I am really talking about is people. 

“Calling for a bigger population, through inward migration and retaining our people, is exactly the same thing as wanting to see the tax base increase.”

READ MORE: Alister Jack accused of 'clear breach' of ministerial code

Tory MSP Liz Smith MSP said: “Independent experts, business groups and various professional associations have all criticised the SNP’s tax plans, and now a senior member of his own party is the latest to attack Humza Yousaf’s dangerous tax and axe budget.

“Scotland is already the highest taxed part of the UK. The SNP’s budget plans would only further widen that gap, creating serious problems in recruiting and retaining people working in Scotland and limiting the potential for Scotland’s economic growth.

“It sounds like Kate Forbes is now recognising the significant and damaging tax burdens that her government has placed on hardworking Scots. She should therefore take a stand and vote down the SNP’s dangerous budget plans.”

The Sunday Times also reported Mr Yousaf may be considering a comeback for Ms Forbes, inviting into his cabinet if health secretary Michael Matheson is forced to resign.

A Holyrood probe is expected to report soon on whether Mr Matheson improperly claimed public money to help cover an £11,000 roaming charges bill linked to his MSP iPad.

The charge was run up on a family holiday in Morocco last year by his sons watching football - something Mr Matheson denied to the press after belatedly learning the truth.