“She perhaps should be spending a little more time learning how budgets work, learning to count and learning to spell before making such an utterly bizarre and personalised attack on me,” said Mr Purvis, who represents Tweeddale, Ettrick and Lauderdale.

His reference to spelling relates to a press release late last week from Ms Grahame which alluded four times to her rival as “Purves”.

Her attack was launched after Mr Purvis, who is his party’s spokesman on finance, signed a letter with Conservative and Labour colleagues asking for the £500million Glasgow project, axed by Scottish finance minister John Swinney last year, to be reinstated. She claimed the letter suggested the cash could be found from existing projects.

“This is a despicable and desperate move that could potentially undermine the Borders railway,” claimed Ms Grahame.

“Mr Swinney has already announced he was scrapping the GARL project due to expected budget overruns and as a direct result of the Treasury in London cutting £500million a year from the Scottish budget.

“Even the dogs in the street know that reinstating GARL would pose a direct threat to the reinstatement of rail to the Borders. Mr Purves [sic] is not prepared to say which projects should have money taken from them to be ploughed into GARL, but he must know that the Borders railway project is at the top of the list amongst his co-signatories to this latest letter.

“This is typical of the Lib Dems, saying one thing nationally and the complete opposite locally. The Liberals’ finance policy is driven by Mr Purves and this latest cynical move by him undermines his credibility locally and raises serious questions over his commitment to the Borders railway and the jobs and investment it will bring.

“I suspect that even for those few people locally who oppose the Borders railway will realise it is better to have the money spent in the Borders than not at all and on that basis, Mr Purves has answers to give to the entire Scottish Borders community.”

Mr Purvis told us: “Dear oh dear. One might have thought that after losing to me twice in the Scottish Parliamentary elections Ms Grahame might have been able to spell my name right.

“One of the reasons why she has failed to win here is her personalised and negative approach. I do support a rail airport link to Scotland’s biggest city, and I was also instrumental in persuading the previous Scottish Government to back the Borders Rail project as well.

“Her SNP Government is choosing to deliver the Borders railway through a public private partnership (PPP) route which will be paid for over 30 years to a private sector consortium currently being advertised for.

“GARL was proposed to be paid out of the completely different capital budget for which all opposition parties, including the Greens, have written asking for more details.