Boris Johnson’s tax plans could spell “disaster” for Scotland’s property market and help boost the drive for Scottish independence, it was claimed today.

The frontrunner to succeed Theresa May has suggested he wants to cut stamp duty land tax in England to help boost a sluggish housing market, especially in London.

Earlier this month, he said: "I think, particularly in London, there is clearly a problem with stamp duty and it needs to be addressed. I'm not going to put a figure on how much we're going to cut but we will certainly be looking to do that because you can do that in such a way as to increase revenues if you get it right because the market is locked up at the moment."

However, it has been suggested that Mr Johnson is looking to raise the current £300,000 threshold, at which stamp duty kicks in, to £500,000, giving a major boost to first-time buyers in England as well as reducing the top level for the most expensive properties from 12 per cent to seven.

Such a move could have political consequences not least in the Midlands and northern England, where average property prices are below £500,000, meaning that most people buying a home would be exempt from the property tax.

However, the former London Mayor’s stamp duty reduction plan could, one leading Scottish property management agency claimed, have unintended consequences; that is, opening up an enormous gulf between the cost of buying a home north of the border and south of it.

David Alexander, joint managing director of the Edinburgh-based Apropos by DJ Alexander Ltd, warned of Scotland facing a “property exodus” should Mr Johnson’s tax plan be implemented. It would, he declared, “prove disastrous for the Scottish property market”.

Mr Alexander said: “The proposal is aimed at injecting some life into the flagging London property sector but would open up an enormous disparity in taxation between Scotland and the rest of the UK.”

He explained that since 2015 when the Scottish Government introduced its own land and property tax – the Land and Buildings Transaction Tax[LBTT] - after responsibility was devolved to Holyrood, Scots have paid £3,350 more than their UK counterparts for a £400,000 home and £8,350 more for a property costing £500,000.

“There is already a financial disparity between the Scottish and UK property markets with markedly higher levels of tax charged on homes north of the border valued at £330,000 upwards. If Boris Johnson’s proposal came into force it would mean that homebuyers in Scotland would be paying £4,600 in LBTT for a £300,000 home and £13,350 in tax for a £400,000 property while people in England paid nothing,” stressed Mr Alexander.

He also seized on Mr Johnson’s plan to raise the threshold for the 40p higher rate of income tax south of the border from £50,000 to £80,000, which, he argued, would “disproportionately punish Scots income and their house-buying costs”.

The property expert went on: “The tax threshold changes would result in Scots earning £80,000 paying £7,844 more in tax per year which, in itself, might be a disincentive to move to Scotland. With property taxes also substantially higher this could result in severe difficulties in attracting individuals and investment to Scotland.”

Mr Alexander also claimed the picture was “even bleaker” under Mr Johnson’s tax plan for second homeowners, landlords and property investors.

He said a £200,000 second property in Scotland would cost the purchaser £9,100 in tax compared to £6,000 in the rest of the UK while for a £400,000 property the differential would be £28,350.

“If this proposal is introduced early in the expected Johnson prime ministership there would be an immediate end to property investment in Scotland,” declared Mr Alexander.

“Why would anyone want to pay so much in taxes when in another part of the UK they would be charged so much less? Under these proposals, investors, second homeowners, and landlords would find everywhere but Scotland a much more attractive place to invest in and would take their money elsewhere. Equally, attracting and keeping wealthy individuals in Scotland will become much more difficult given the higher personal taxes and the very high cost of property purchase.”

He added that the Johnson proposal would simply accelerate the financial divergence that was already happening between north and south of the border and would make “Scotland a much more difficult and costly place to live and invest”.

An SNP spokesman said: “These claims obviously do not take into account the fact that people pay hundreds of thousands of pounds more in London than they would for similar property in Scotland – and if Boris Johnson is going to base all of his policies around what is right for London, then he is simply making the independence argument for us.

“The SNP’s residential LBTT reforms mean that more than 80 per cent of taxpayers have either paid less tax compared to Stamp Duty Land Tax or no tax at all.

“Despite repeated unfounded criticisms, the outlook for LBTT is positive; receipts to grow each year, property prices and transactions to rise each year. Revenue is forecast to be up £178m over the five-year forecast period.”

Christine Jardine for the Liberal Democrats said: “Boris Johnson has once again demonstrated his complete ineptitude. This is not the first time he has announced a policy over the course of this bleak Tory leadership contest without considering the implications for the whole country.

“People deserve better than a potential prime minister blundering from one announcement to the next,” added the Edinburgh MP.

The Johnson camp was approached for a comment about the fears raised about the Tory leadership candidate’s property tax plans but there was no response.