Vote Leave has been fined £61,000 for breaking electoral law over the 2016 EU referendum.

The official campaign for Brexit, which was supported by senior political figures including Boris Johnson and Michael Gove, was found by the Electoral Commission to have failed to declare money it spent on the controversial data firm Aggregate IQ.

Here’s all you need to know on Vote Leave and the commission’s decision:

What is Vote Leave?

Vote Leave was the officially designated Brexit-supporting campaign during the 2016 EU referendum. It was supported by high-profile figures including ex-foreign secretary Boris Johnson and the current Environment Secretary Michael Gove and a whole host of high-profile Tory Brexiteers, with Labour’s Gisela Stuart as chairwoman. It was behind the infamous Brexit bus, adorned with “We send the EU £350 million a week, let’s fund our NHS instead”, a figure since discredited.

What is a lead campaigner?

In April 2016 – two months before the referendum vote – the Electoral Commission designated a lead campaign group on each side. These two groups had a spending limit of £7 million for campaign activity. Other registered groups were limited to the lower total of £700,000 and unregistered campaigners limited to £10,000.

What did Vote Leave do wrong?

It linked up with a small unregistered group, BeLeave, run by a then student called Darren Grimes, to spend more than £675,000 with Aggregate IQ, a Canadian data firm with links to Cambridge Analytica, which is at the heart of a probe over social media message targeting during the campaign.

EU referendum
Darren Grimes, pictured back left behind Michael Gove, was fined £20,000 and referred to the Metropolitan Police by the Electoral Commission (Stefan Rousseau/PA)

How much did Vote Leave spend?

Taking in the £675,000 which should have been declared, the commission said they spent £7,449,079, breaching the limit by almost £500,000. It also incorrectly reported £234,5012 and there were missing invoices for £12,849.99.

What does the law say about referendum spending?

The Political Parties, Elections and Referendums Act of 2000 (PPERA) makes it an offence to exceed campaign spending limits or to fail to provide full and accurate reports of spending.

How much were they fined?

They were fined £21,000 for two offences of failing to submit a complete spending return, and a further £20,000 for each of two more offences, breaching the spending limit and failing to produce documents by a specified date. They were fined a total of £61,000. Mr Grimes was fined £20,000 for exceeding the statutory limit for a non-registered campaigner. He was also found to have failed to submit a complete spending return but faced no extra penalty.

Is there any criminal offence?

Mr Grimes and David Halsall, Vote Leave’s “responsible person”, have both been referred to the Metropolitan Police “in relation to false declarations of campaign spending”, the Commission said. It has also shared its investigation files “in relation to whether any persons have committed related offences which lie outside the Commission’s regulatory remit”.

What does Vote Leave have to say?

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

It accused the official agency of being “motivated by a political agenda” and basing its conclusions on “unfounded claims and conspiracy theories”.