Independent MEP Luke 'Ming' Flanagan says his Twitter account was hacked after it posted a late night comment about naked photographs of former Green Party candidate Saoirse McHugh.
The claim came after his account tweeted "Sapirse mchugh photo skinny dipping" at 2.50am on Monday.
The post has since been deleted but screen grabs of the comment have been shared online by other Twitter users.
The comment may be a reference to photos of Ms McHugh swimming which previously appeared in The Guardian newspaper.
Yesterday afternoon, Mr Flanagan posted a comment explaining he believed his account had been hacked.
"Have just changed my password. I believe my account was compromised.
"I am contacting Twitter to establish what has happened. Some nasty people out there. Mind yourselves," he wrote.
When contacted about Mr Flanagan's claim that his account had been compromised, a Twitter spokesperson said: "We've nothing to share here."
Ms McHugh told The Herald Mr Flanagan contacted her yesterday to tell her about the situation. She wasn't aware of the issue before this.
The former Green Party candidate said she accepts Mr Flanagan's explanation.
"I believe him and I don't think there's anything more to say about it," she said.
Mr Flanagan is a close political ally of Ms McHugh and campaigned for her in February's general election. She was unsuccessful in the last European and general election.
Earlier on Sunday evening Mr Flanagan posted tweets that were supportive of Ms McHugh during an exchange she was having with the Irish Farmers' Association.
She had responded to an IFA post about a European Court ruling that means plant-based foods can't be described as milk.
She tweeted the IFA saying: "If you can milk a tired and boring talking point you can milk an oat."
The IFA responded saying: "Interesting.... wonder if you'd have been so dismissive of the ECJ if you were elected as an MEP??? I guess we'll never know".
Mr Flanagan later posted: "Saoirse got more votes than your organisation has real members."
He added: "She has more integrity in her smallest finger nail than your whole organisation. She'll be an MEP yet. We'd be lucky to have her."
Earlier this year, Mr Flanagan hit the headlines when he joined a video conference meeting of the EU Agriculture Committee wearing just a shirt and underpants.
He was participating in the Agriculture Committee's meeting to debate the EU's long-term budget.
But when his remote camera was activated, he could be seen sitting on a bed wearing a shirt and underpants.
He could be seen rubbing his upper leg as he said to the committee: "We read in some European newspapers how this money will be broken down state-by-state.
"Where can MEPs get definitive information on this rather than reading it second-hand from European journalism?"
Mr Flanagan said he had just returned from a run and put on a shirt but did not put on trousers for the meeting with his EU counterparts.
The MEP made light of the incident on Twitter after video footage of him in his underwear was shared online.
Retweeting the video of him, he told Wexford MEP Mick Wallace, who is known for his colourful shirts, "I'll see your pink shirt and raise you a pair of underwear Mick".
Mr Flanagan has been twice elected to the European Parliament in Midlands North West.