Croydon Central MP Gavin Barwell has denied breaking electoral laws after it emerged he is being investigated by the Metropolitan Police over his campaign spending in the run-up to last year’s general election.

The probe was launched following a complaint by one of Mr Barwell’s constituents, who alleged the Conservative MP failed to declare expenses that would have taken him above legal spending limits before last May’s polls.

He defeated his Labour challenger Sarah Jones by just 165 votes in one of the most tightly contested seats in the country at the general election.

Today the MP, whose spending was £252 below the limit by the end of the campaign, insisted he had done nothing wrong, adding: “I’m confident we have observed the law.”

Mr Barwell, who in March published a memoir about his knife-edge contest with Mrs Jones, is one of dozens of Conservative MPs across the country under investigation for allegedly failing to declare campaign expenses.

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While many of the allegations concerned use of the party’s “battle bus” volunteers, the accusations against Mr Barwell are thought to relate to spending on his campaign office and leafleting.

His expenses show he spent just £71.76 – the equivalent of £1.84 per day - on renting out office space at the Croydon Conservative Federation in Purley during last year’s “short campaign” election period - the 39 days before the May 7 vote.

The MP said the sum represented the "notional" value of the office, owned by the party and which he shared with Croydon’s two other Conservative Parliamentary candidates.

He claimed the expense as “business rates” because he did not pay rent for the office, and acknowledged it would have cost “significantly more” to open a separate campaign office in his constituency.

Mr Barwell added: “There’s obviously a significant benefit if you open a shop-front office in the constituency - but there’s also a significant cost.”

The MP also dismissed the suggestion that thousands of undelivered leaflets printed for his campaign should have been included in his election expenses.

He said: “If you don’t put stuff through people’s door, how does that influence people? Where do you draw the line?”

Asked whether he believed campaign spending laws needed revising, Mr Barwell declined to comment.

Campaign over-spending is a criminal offence punishable by up to a year in prison.

A Metropolitan Police spokeswoman confirmed the force had “received complaints regarding possible irregularities in relation to election expenses returns for 2015.”

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She added: “This matter is currently subject to assessment by officers from the special enquiry team.”

Mr Barwell said police had written to him informing him of the investigation.

It is not the first time the MP’s campaign spending has been the subject of a criminal investigation. In 2010 he was forced to apologise after it was revealed he failed to declare some of his leaflet expenditure.

Sarah Jones, Labour’s narrowly defeated challenger in Croydon Central last May, has been contacted for comment.

But Mr Barwell does not think the latest allegations has come from his political rival and said he believed a National Front member had complained to the police.

Asked if he was worried about the outcome of the Met’s investigation, Mr Barwell said: “I’m confident the election expenses are an accurate record of what we spent on the campaign.”

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