BREXIT campaign group Leave.EU has been reported to police over the organisation’s spending in the run up to the 2016 referendum.

The Electoral Commission handed down a hefty £70,000 fine, and accused the Leave-backing activists of spending at least 10 per cent more than they were legally allowed to.

The commission said the actual overspend figure “may well have been considerably higher”, adding that the group had presented “incomplete and inaccurate” information.

Leave.EU, was co-founded by former Ukip backer Arron Banks, and was fronted by Nigel Farage.

They were responsible for the Breaking Point poster that was reported to police and accused of inciting racial hatred and breaching UK race laws.

Yesterday, it was chief executive, Liz Bilney, who took the fall. The commission referred her to the Metropolitan Police, saying they had “reasonable grounds to suspect that the responsible person for Leave.EU committed criminal offences”.

Scotland Yard confirmed they were investigating a potential criminal offence under section 123(4) of the Political Parties, Elections and Referendums Act 2000.

Banks attacked the regulator, describing them as a “Blairite swamp creation packed full of establishment remoaners that couldn’t quite make it to the House of Lords”.

“We view the Electoral Commission announcement as a politically motivated attack on Brexit and the 17.4 million people who defied the establishment to vote for an independent Britain,” Banks said.

He added: “The EC went big-game fishing and found a few ‘aged’ dead sardines on the beach. So much for the big conspiracy. What a shambles. We will see them in court.”

Banks told the BBC he would be launching a legal challenge against the report.

The £70,000 fine handed out by the Electoral Commission matches its previous record financial censure, given out in March 2017 to the Tories for offences during the 2015 general election campaign and by-elections the previous year.

Bob Posner, the commission’s director of political finance and regulation and legal counsel, said it would have been much higher, but the law caps how much the watchdog is allowed to fine.

He said: “The rules we enforce were put in place by Parliament to ensure transparency and public confidence in our democratic processes. It is therefore disappointing that Leave.EU, a key player in the EU referendum, was unable to abide by these rules. Leave.EU exceeded its spending limit and failed to declare its funding and its spending correctly. These are serious offences. The level of fine we have imposed has been constrained by the cap on the Commission’s fines.”

A separate probe into spending by the official Leave campaign, Vote Leave, is continuing.

The Commission said Leave.EU had not disclosed £77,380 of fees paid to the company Better For The Country Limited, the campaign organiser.

The commission investigation also found that three loans from Banks, totalling £6 million, had been incorrectly reported by Leave.EU.

It was also criticised for failing to report services from US strategy firm Goddard Gunster when it should have done.

The organisation additionally failed to provide invoices or receipts for a further 97 payments of more than £200, which together totalled £80,224.

But the commission said it found no evidence that controversial tech firm Cambridge Analytica had made donations or provided paid-for services, and its role was limited to “initial scoping work”.

Though the report does say the data firm tried to obtain and were repeatedly promised contracted work.