POLICE have been asked to investigate whether the Liberal Democrats spent more than the legal campaign limit in one of the toughest contests of the General Election

A member of the public yesterday submitted a detailed complaint asking officers to check whether an inaccurate spending return was filed in respect of Edinburgh West.

It is a criminal offence punishable by a year in jail to knowingly submit an inaccurate return.

The seat was won by LibDem Christine Jardine, who claimed she spent less than her SNP rival, despite local voters being deluged by LibDem newsletters, leaflets and letters.

A former BBC reporter, Ms Jardine, 56, vehemently denies any wrongdoing and claims she is being smeared by the SNP simply because she beat them.

The development emerged as Sir Vince Cable, the UK leader of the LibDems, strongly defended Ms Jardine and his deputy Jo Swinson over their spending on a visit to Edinburgh.

The SNP had questioned whether the pair’s official spending declarations were reliable, but Sir Vince insisted they were beyond reproach and his party had “nothing to apologise for”.

He said: “My understanding is it's absolutely completely above reproach, that there's absolutely no question of any impropriety.

“It's a complex process, apportioning costs, but the party has followed advice.

"There's no question of anything wrong whatsoever, nothing to apologise for."

Ms Swinson and Ms Jardine are facing questions after the Herald revealed they disregarded thousands of pounds of leaflet costs on their official candidate declarations.

The MPs disregarded £4000 and £3000 respectively on the basis it was “national” spending, and promoted the LibDems in general, rather than local campaign expenditure.

If the sums had been counted as local spending, it would have put both Ms Swinson and Ms Jardine well above the legal spending caps imposed to ensure a fair contest.

The Electoral Commission allows the splitting of leaflet costs into local and national on the basis of an “honest assessment”, but says the “main purpose” of the material is key.

It warns: “You should not split costs if an item is produced mainly to promote a candidate, and uses the party’s name or refers to the party’s policies purely in support of that aim.”

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.

Earlier, Ms Jardine told BBC Radio Scotland spending rules were followed “to the letter”.

She said the SNP were still "slinging mud" after losing the seat, adding: "This is simply an exercise in reputational damage to try and smear me as the candidate who beat them.”

Edinburgh West was LibDem-held from 1997 to 2015, when it was won by the SNP’s Michelle Thomson, and the LibDems made retaking it a priority in the General Election.

After some of the nastiest campaigning in the country, with an SNP activist repeatedly trolling Ms Jardine on Twitter on the day of her husband’s funeral, she won by 2988 votes.

SNP MP Pete Wishart said there was an “extremely worrying pattern” in LibDem spending.

He said: “Vince Cable needs to get a grip and explain how widespread these practices are.

“The Lib Dems must start being transparent about what they spent in constituencies across Scotland or else we’ve got an emerging election expenses scandal on our hands.

“There is an overwhelming public interest in getting to the bottom of this.”

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.

A LibDem spokesperson said: “All expenditure in this election was reported correctly and appropriately in line with specific advice given to us by the Electoral Commission and the law. We are confident in these election returns."