MP Christine Jardine has denied playing “fast and loose” with election rules and said she is the victim of an SNP smear after questions were raised about her campaign spending.

Ms Jardine, who gained Edinburgh West for the Liberal Democrats in June, strongly defended her record after an investigation by the Herald into her official declaration.

The former BBC reporter said £3000 of her election material costs were “national” rather than local, as the spending promoted the LibDems in general, not her as a candidate.

It meant that, despite the LibDems deluging houses with leaflets, Ms Jardine reported spending less than her Nationalist rival for the seat, something the SNP say defies belief.

The LibDem material included double-sided leaflets with Ms Jardine on one side and Scots leader Willie Rennie on the other, which were split 50-50 between local and national totals.

The Electoral Commission allows split spending, but says the “main purpose” is key.

Its guidance says the cost of leaflets which promote a specific candidate, and which include generic party references purely to support that promotion, should not be split.

If the £3000 of national costs had been counted towards Ms Jardine’s local total, it would have put her around £1350 about the legal spending cap of £12,995.

No other candidate, of any party, in any Edinburgh seat, split their costs in this way.

Ms Jardine insisted: “If it had been local expenditure it would have been accounted for as local expenditure.

“It was national expenditure and therefore it was counted as national expenditure.”

The Herald has also seen personalised mail sent by LibDem HQ in London to voters in Edinburgh West which was not included in Ms Jardine’s total, despite the local targeting.

One letter from Mr Rennie mentioned Edinburgh West five times.

UK LibDem deputy leader Jo Swinson is also facing questions over her spending in East Dunbartonshire at the election, where she reported coming £210 under the legal limit, but only after disregarding £4000 of “national” costs and saying £2700 of leaflets were unused.

Edinburgh West, which was LibDem-held from 1997 to 2015 until it was won by the SNP’s Michelle Thomson, was one of the LibDems’ top targets in the General Election.

After one of the roughest fights in the country, with an SNP activist repeatedly trolling Ms Jardine on the day of her husband’s funeral, she won by 2988 votes.

Ms Jardine, 56, told BBC Radio Scotland’s Good Morning Scotland programme that she and her party had followed the spending rules “to the letter” and properly accounted for all costs.

She said: “As a journalist, I have to say it’s one of the weakest stories I’ve ever seen, and strikes me as nothing more than an exercise in reputational damage.

“The SNP, having lost the seat, where they ran the dirtiest campaign I have seen for many years, that was all about slinging mud, and this is simply an exercise in reputational damage to try and smear me as the candidate who beat them.”

Asked about the personalised mail absent from her invoices, she said: “Everything which we sent out was accounted for in our filing.”

Asked if the LibDems were playing “fast and loose with the rules”, she said: “No, we’re not. We’re following the rules to the letter.

“This is nothing more than an exercise in reputational damage by the SNP because they lost the seat.”

The LibDem MSP for Edinburgh Western, Alex Cole-Hamilton, who was a key member of Ms Jardine’s campaign effort, is currently the subject of a police report to the procurator fiscal over his 2016 Holyrood spending, after he split his costs in myriad ways.

It is an offence punishable by a year in jail to knowingly file an inaccurate spending return.

Ms Jardine denied her party had a “problem” with observing the rules.

She said: “I’m perfectly happy for my spending on the election to be examined by the Electoral Commission. That’s what the Electoral Commission is for.”

The Commission said complaints about election spending were in fact a police matter.

After the 2015 General Election, the UK LibDems were fined a maximum £20,000 after failing to declare more than 300 items of expenditure worth almost £190,000.

Toni Giugliano, the defeated SNP candidate in Edinburgh West, said local voters would be "amazed that the LibDems claimed to have spent less than the SNP, given the deluge of leaflets from their London HQ and their Corstorphine office costs.

"If they’d lodged their expenses in the way I did – recording 100 per cent of local leaflets – it appears they’d be well over the legal limit."