Claims Vote Leave broke law 'utterly ludicrous' says Boris Johnson

Whistleblower Shahmir Sanni, who worked on the campaign, claimed Vote Leave used BeLeave to get around strict spending limits set by the Electoral Commission.

Vote Leave has strongly denied wrongdoing and said the £625,000 (€715,000) donated to BeLeave was within the rules.

But Mr Sanni told Channel 4 News: "I know that Vote Leave cheated ... I know that people have been lied to and that the referendum wasn't legitimate."

Cabinet ministers Mr Johnson, Michael Gove and Chris Grayling were among senior politicians involved in the Vote Leave campaign.

Foreign Secretary Mr Johnson said Channel 4 and Observer stories based on Mr Sanni's testimony were "utterly ludicrous" and Vote Leave "won fair and square - and legally".

Mr Gove, who was campaign co-chair for Vote Leave, said the result of the referendum must be respected.

"I respect the motives and understand the feelings of those who voted to remain in the EU," he said.

"But £17.4 million opted to leave in a free and fair vote and the result must be respected. It's our job now to work to overcome division."

Deputy Labour leader Tom Watson told BBC1's Andrew Marr Show: "Theresa May needs to make sure the Electoral Commission has the resources to fully investigate the allegations made that there was criminal collusion.

"Because let's remember, the people that led these campaigns are now senior Cabinet members, and I think we need to make sure that they were not aware of what was going on, and that's why I think the resources are needed, and if needs be the police should be resourced to investigate as well."

Liberal Democrat Brexit spokesman Tom Brake also suggested the police should be called in.

The allegations centre on Mr Sanni's claims that BeLeave was controlled by Vote Leave rather than an independent campaign.

Mr Sanni said: "In effect they used BeLeave to over-spend, and not just by a small amount ... Almost two-thirds of a million pounds makes all the difference and it wasn't legal."

Mr Sanni was in a relationship with senior Vote Leave figure Stephen Parkinson - now Theresa May's political secretary - at the time of the referendum and claimed through his lawyers he was "outed" by the Number 10 aide in the run-up to the Channel 4 disclosure.

Mr Parkinson said he was "saddened" by the "factually incorrect and misleading" statements by Mr Sanni and his lawyers.

He said: "I cannot see how our relationship, which was ongoing at the time of the referendum and which is a material fact in the allegations being made, could have remained private once Shahmir decided to publicise his false claims in this way."

Mr Parkinson said he had no responsibility for digital campaigning or donations on the Vote Leave campaign and was "confident that I stayed within the law and strict spending rules at all times".

Commons Leader Andrea Leadsom told Sky News' Sunday with Niall Paterson it was an "incredibly difficult area" but "Stephen Parkinson has said the reason for his statement was because the context of the background of these allegations is very important".

Health and Social Care Secretary Jeremy Hunt defended Mr Parkinson as "someone of the highest integrity", adding "there are two sides to these stories".

He told ITV's Peston on Sunday: "The critical question here is - first of all - was the campaign properly conducted? Also, did anything that happened that shouldn't have happened - if that was the case - actually affect the result?"

Tory MP Heidi Allen told Peston on Sunday: "The whole thing feels pretty filthy and when you mix personal relationships and works it can get messy, as it has done here."

She said the row over Mr Parkinson and Mr Sanni's relationship "feels like a bit of a smokescreen" and "you need to separate the gossip and the discrediting from what actually happened".

An Electoral Commission spokeswoman said: "The commission has a number of investigations open in relation to campaigners at the EU Referendum; it does not comment on live investigations."

- PA