Independent MEP Luke 'Ming' Flanagan has said Belgian police are investigating the reported hacking of his Twitter account.
Earlier this week the Ireland North-West MEP claimed his account had been compromised after a late night post about former Green Party candidate Saoirse McHugh.
He said that he had to change his password and was contacting Twitter to establish how it happened.
In a statement today, Mr Flanagan described the incident as a "malicious act of vandalism on my good name".
He said that the European Parliament's Directorate-General for Security and Safety (DG SAFE) is helping him with a police investigation.
The MEP said that the unauthorised use of his Twitter account had taken place from a location in Belgium.
He said his parliamentary assistant and an investigator from DG SAFE met Belgian Police on Wednesday.
The statement says: "I have now established that my Twitter account had been logged into on a third party app called Tweetcaster.
"This app allowed an individual to tweet from my account using an old password."
Mr Flanagan goes on to say that the app was used twice to access his Twitter account from Belgium on Monday 28 September.
He said this was the same day that an unauthorised tweet was posted and then deleted from his account.
The statement said: "At the time the tweet was posted and then deleted, I was in Ireland and have been since March of this year due to Covid-19 restrictions."