- Video report by ITV Political Correspondent Daniel Hewitt
Nigel Farage will be investigated by a European Parliament committee after a complaint was made about his alleged failure to declare payments of £450,000 from Arron Banks.
A complaint about The Brexit Party leader was submitted to European Parliament president Antonio Tajani by Liberal Democrat MEP Catherine Bearder.
Under European parliament rules, MEPs must declare payments made to them, or other support given by third parties.
Mr Farage admitted he did not declare the sum to the European Parliament because he was about to leave politics and seek a new life in the US.
The Electoral Commission visited the offices of the Brexit Party to review how the party receives funds, but said in a statement on Tuesday evening it has "not seen evidence of electoral offences."
A Electoral Commission spokesperson said: "We have not seen evidence of electoral offences, but the law in this area is complex and we want to satisfy ourselves that the Party’s systems are robust."
Tuesday visit's was to take "a closer look at the systems the Party has in place to receive funds" and was part of "active oversight" of donations, the spokesperson added.
Nigel Farage has denied allegations of any wrongdoing, telling supporters in Wakefield, Yorkshire, on Monday that money for the party had been raised by 110,000 people paying a £25 fee.
Asked by ITV News if he was 100 per cent confident he had not received a single penny from foreign donations, Mr Farage replied: "I can be 99 per cent confident."
The European Parliament incident has been referred to a committee, but that will not sit until June 4 at the earliest - after this month's European elections.
Mr Farage will be invited to comment before the committee makes a recommendation on possible sanctions.
Payments from Mr Banks, founder of Leave.EU, to Mr Farage were revealed by a Channel 4 News investigation.
Since the revelation, Mr Farage has banned Channel 4 from attending Brexit Party events.
A spokesman for the Electoral Commission said Tuesday's visit was part of its "active oversight and regulation" of donations.
They said: “The Brexit Party, like all registered political parties, has to comply with laws that require any donation it accepts of over £500 to be from a permissible source.
“It is also subject to rules for reporting donations, loans, campaign spending and end of year accounts. We have already been talking to the party about these issues.
“As part of our active oversight and regulation of these rules, we are attending the Brexit Party’s office tomorrow to conduct a review of the systems it has in place to receive funds, including donations over £500 that have to be from the UK only.
“If there’s evidence that the law may have been broken, we will consider that in line with our Enforcement Policy."
Gordon Brown takes aim at Farage
It comes after former Prime Minister Gordon Brown took aim at Farage's Brexit Party for receiving large quantities of money via small "undeclared, untraceable payments".
Under current rules, donations under £500 given to political parties do not have to be declared.
Official donations of £500 or more must be made by a "permissible donor" who is on the UK electoral roll or a business registered at Companies House which is operating in the UK.
Farage fired back at Brown's remarks, calling them an "absolutely disgusting smear".
Mr Brown voiced his concerns during a Labour rally in Glasgow and claimed the Brexit Party was a private company made up of shareholders, adding: ''You can pay to this party in Russian roubles, American dollars, Malaysian ringgit and, of course, probably to his disdain, euros as well.''
Mr Brown raised concerns over the method of payment used to process donations by supporters of the party.
He said: “Now we find the Brexit Party that has been formed is not a party, it’s actually a private company. It doesn’t have members, it has shareholders.
“The key shareholder, with the controlling interest, is Nigel Farage. And you pay money not to become a member, but to become a supporter, and you pay through PayPal and you cannot discover whether the money is coming from foreign sources or British sources."
Mr Brown added: “If this election is about trust in democracy, the Electoral Commission has the power before Thursday to tell us if they’ve had questions answered about where the money is coming from, who is giving the money, whether the money is coming from foreign sources, including America and Russia, and whether rules are being broken.
“This is a not a party in the ordinary sense, this is a private company. It’s run by Nigel Farage, donations go through PayPal, and he’s not going to be remembered as he wants, as the man of the people.
"He’ll be remembered as the man of the PayPal, because that’s where the money’s coming from.”
Mr Brown continued by challenging the Electoral Commission to indicate before Thursday whether they are investigating, or if questions on the “dubious issues” around such transactions had been answered.
He said: “Democracy is ill-served and trust in democracy will continue to be undermined if we have no answers to where the money is coming from and why these declarations to the European Parliament have never been made.”
Mr Farage has denied any wrongdoing.