The controversial former Ukip leader will lose £35,000 in total after European auditors alleged he had misspent money meant for his EU office, according to the Guardian.
The British daily The Guardian reported on Friday that auditors found that Farage previous year had used his parliamentary allowances to pay an assistant who was actually working for his party in Britain instead of doing parliamentary work in Strasbourg.
"By even publicly floating the idea of a second referendum Nigel Farage has effectively joined the Remain camp". Mr Adams was Ukip's national nominating officer and was described as one of its "key people".
European Union auditors said they did not believe that Mr Adams was working on issues related to Mr Farage's work as an MEP.
Mr Helmer denied any wrongdoing but gave no explanation as to why he was stepping down.
Two investigations were closed without any formal action.
A spokesman for the Eeuroskeptic Europe of Freedom and Direct Democracy Group (EFDD) told the Independent: "There is a vindictive campaign by the European Parliament of selective persecution of Euroskeptic MEPs, parties and groups".
Under EU rules, full-time MEP assistants are not allowed to do paid work for a national political party.
"For perhaps the first time in his life, Nigel Farage is making a valid point", said Labour MP Chuka Umunna, a leading supporter of the pro-EU Open Britain campaign group. Part-time assistants need to have second jobs, paid and voluntary, vetted by European parliament authorities to prevent a conflict of interest.
But, if MEPs fail to "provide any justification or proof" that their funded assistants are only carrying out EU-related duties, "then the administration may recover the money by withholding part of the MEP's salary".
Marine Le Pen is under formal investigation by French magistrates, after she refused to repay almost €300,000 of EU funds, following a European parliament investigation into EU funds spent by the far-right Front National leader.