THE official Brexiteer campaign organisation for the 2016 referendum has been referred to the police for a criminal investigation and fined tens of thousands of pounds.

Vote Leave, which was fronted by senior politicians including Boris Johnson and Michael Gove, failed to declare money it spent with controversial data firm Aggregate IQ, the election watchdog concluded.

The Electoral Commission said its inquiry found “significant evidence” of joint working – in breach of rules – between Vote Leave, which has been fined £61,000, and youth Brexit group BeLeave, which was founded by student Darren Grimes.

Grimes was fined £20,000 and referred to the Metropolitan Police along with David Halsall, the person responsible for Vote Leave, “in relation to false declarations of campaign spending”, the commission added.

The commission’s investigation also found Vote Leave returned an incomplete and inaccurate spending report, with nearly £234,501 reported incorrectly, and invoices missing for £12,849.99 of spending.

The findings sparked calls from Remain-supporting MPs from across the political spectrum for another referendum, either a reply of the original or a second vote on the terms of the Brexit deal.

The commission also found a donation of almost £680,000 made by Vote Leave to BeLeave was spent with Aggregate IQ “under a common plan with Vote Leave”, and should have been declared. This spending took Vote Leave over its £7 million legal limit by almost £500,000.

Bob Posner, Electoral Commission director of political finance, said: “We found substantial evidence that the two groups worked to a common plan, did not declare their joint working and did not adhere to the legal spending limits.

“These are serious breaches of the laws put in place by Parliament to ensure fairness and transparency at elections and referendums.”

Vote Leave was the official registered Brexit-supporting campaign group for the 2016 referendum.

As well as Johnson, the former foreign secretary, and Gove, the Environment Secretary, it was supported by MPs including Transport Secretary Chris Grayling, International Development Secretary Penny Mordaunt, her predecessor Priti Patel, and the new Brexit Secretary Dominic Raab.

Leading Labour Brexiteer Gisela Stuart was chairwoman.

The original allegations against the campaigns came from information provided by whistleblowers including Christopher Wylie and Shahmir Sanni, who alleged the money was used to pay Aggregate IQ for targeted messaging services on Facebook and other social media.

Wylie worked for Cambridge Analytica, the data firm at the centre of the Facebook privacy scandal, while Sanni worked with BeLeave.

Vote Leave is the latest Brexiteer referendum organised to be found in breach of electoral rules by the commission. In May, Leave.EU was fined a record-equalling £70,000 and its chief executive Liz Bilney referred to police over its spending.

Vote Leave said the report contained “a number of false accusations and incorrect assertions that are wholly inaccurate and do not stand up to scrutiny”.

Labour’s Chuka Umunna, who raised an Urgent Question in the Commons yesterday, told MPs the findings of the Electoral Commission were “shocking” and said Vote Leave’s actions were an “affront to our democracy”.

Tory MP Sarah Wollaston added: “We cannot have confidence that this referendum was secure and it should be re-run.”

The findings focussed attention again on donations made to the Scottish Tories. Pete Wishart, the SNP MP, renewed calls for the commission to investigate funding from the secretive Scottish Unionist Association Trust to Ruth Davidson’s party.