The Electoral Commission has written to Zac Goldsmith to tell him about its “concerns” over his election spending - but said the case was not serious enough to refer it to police.

The independent watchdog, which reports directly to Parliament, said the Richmond and north Kingston MP’s returns had been “unclear in places”.

It said the way Mr Goldsmith split his costs between his 2010 parliamentary campaign and the concurrent Richmond Council elections was “not consistent with the commission’s guidance or good practice”.

The Electoral Commission’s report, published today, said: “Had the costs been apportioned in a way more consistent with our guidance, Mr Goldsmith would have exceeded the spending limit for the short campaign, though not the aggregate limit for both campaigns.”

The MP said in July the commission would not find any wrongdoing in its review, which followed a joint investigation by Channel 4 and the Bureau of Investigative Journalism.

They had raised questions about whether the Conservative MP kept within the £11,003 limit during the 23-day run-up to polling day, as suggested in his returns.

The commission carried out a review into whether Mr Goldsmith had left out or under-reported some costs and made a false declaration about his election expenses.

It looked at how much he spent on leaflets, promotional jackets and stickers, campaign boards and hire costs for electric trikes.

It concluded Mr Goldmsith had overspent by £966 on his "short campaign" - the last weeks before polling day - but found his total expenditure was within the aggregate limit “even when the potential under reporting is included”.

Speaking after today's announcement, Mr Goldsmith said: “My campaign team played by the rules, and we knew we would be cleared, but it’s a relief all the same. I do think the rules are horribly complicated, and they need to be much, much clearer for the sake of future candidates.

“The Electoral Commission has found that our overall total election spending came in less than the cap. My political rivals would have had access to all the figures from the day of the election, and none raised any concerns.”

The Electoral Commission’s report said: “In determining whether to refer the case to the police for criminal investigation, we considered not just whether an overspend may have occurred, but also the relative amount involved and whether the aggregate expenditure for both the whole campaign period exceeded the overall spending limit.

“We also considered whether there was any evidence of excessive spending which was so unreasonable as to indicate a deliberate avoidance of the rules.

“Taking all of the circumstances of this case into account including the relative amount of the potential overspend, the fact that the aggregate spending limit was not exceeded and the absence of any evidence of intentional circumvention of the rules, we do not consider that a referral to the police is appropriate.

“We have however written to Mr Goldsmith and Mr Newman to inform them of our concerns about the way some costs were apportioned and have suggested a meeting with [David] Newman [his agent] to discuss our concerns.”

Iain Overton, managing editor of the Bureau of Investigative Journalism, said: "The Bureau of Investigative Journalism welcomes the Electoral Commission's findings into Zac Goldsmith's 2010 election expenses.

“Their conclusion that Mr Goldsmith's apportioning of election costs are a cause for concern and that he may have overspent in his 'short campaign period' shows our investigation was both warranted and necessary."

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