The official Brexiteer campaign organisation at the 2016 referendum has been fined tens of thousands of pounds and senior figures referred to the police for breaking UK electoral law.
Vote Leave, which was supported by senior politicians including Boris Johnson and Michael Gove, failed to declare money it spent with controversial data firm Aggregate IQ, the UK’s Electoral Commission said.
The decision sparked calls from Remain-supporting MPs from across the political spectrum for another referendum, either a replay of the original or a second vote on the terms of the Brexit deal.
The commission said its investigation found “significant evidence” of joint working between Vote Leave – which has been fined £61,000 – and youth Brexit group BeLeave, which was founded by student Darren Grimes.
Mr Grimes was fined £20,000 and referred to the Metropolitan Police along with Mr David Halsall, the responsible person for Vote Leave, “in relation to false declarations of campaign spending”, the Commission added.
The Commission found that 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 spending 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 Mr Johnson, the former foreign secretary, and Mr Gove, the current Environment Secretary, it was supported by MPs including Transport Secretary Chris Grayling, International Development Secretary Penny Mordaunt and her predecessor Priti Patel, the new Brexit Secretary Dominic Raab, with leading Labour Brexiteer Gisela Stuart as 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.
Mr Wylie worked for Cambridge Analytica, the data firm at the centre of the Facebook privacy scandal, while Mr Sanni worked with BeLeave.
Vote Leave is the latest Brexiteer referendum group to be castigated by the Commission after Leave.EU was fined a record-equalling £70,000 and its chief executive Liz Bilney referred to police in May over its spending.
Vote Leave said the Electoral Commission’s report contained “a number of false accusations and incorrect assertions that are wholly inaccurate and do not stand up to scrutiny”.
A spokesman accused it of ignoring “wrongdoing” by Remain campaigners, adding: “All this suggests that the supposedly impartial Commission is motivated by a political agenda rather than uncovering the facts.”
He also reiterated the claim that the Commission failed to interview anyone from the campaign despite them being “willing to do so”.
But the Electoral Commission report said it asked Vote Leave on numerous occasions between November 2017 and February to attend an interview, but it did not do so.
Mr Posner added: “Vote Leave has resisted our investigation from the start, including contesting our right as the statutory regulator to open the investigation.”
“It has refused to co-operate, refused our requests to put forward a representative for interview, and forced us to use our legal powers to compel it to provide evidence.”
Mr Grimes said the fine was “entirely disproportionate and unjustified”.
He added: “I did nothing wrong. I have been persecuted for over two years by powerful people for nothing more than engaging in the democratic process and having the temerity to be on the winning side.”
Labour’s Chuka Umunna, who raised an Urgent Question in the Commons on Tuesday, told MPs the findings of the Electoral Commission were “shocking” and said Vote Leave’s actions were an “affront to our democracy”.
Conservative former minister Sir Nicholas Soames called for the electoral system to be “blown up and started all over again”.
Tory Health and Social Care Select Committee chairwoman Sarah Wollaston added: “Consequences must follow, we cannot have confidence that this referendum was secure and it should be re-run.”
Liberal Democrat Brexit spokesman Tom Brake said the public had been “cheated” and the ruling “strengthens the need for a vote on the deal and an opportunity for the country to escape this mess”.
Asked whether Theresa May still believed that the referendum was free and fair, the Prime Minister’s official spokesman said: “The PM is absolutely clear that this was the largest democratic exercise in our country.”
“The public delivered a clear verdict and that is what we are going to be implementing.”
Commons’ Digital, Culture, Media and Sport Committee chairman Damian Collins said it would probe ways of strengthening the Commission’s powers in its investigation into the use of data in the referendum.