The disappearance of a man more than a decade ago was more likely foul play than choice, police now believe as they plead for help in solving the mystery.

The last confirmed sighting of then-55-year-old Brendan Breen was in Melbourne on April 12, 2012.

His former partner reported him missing almost a month later, on May 9, when he cancelled dinner plans with her at the last minute via text and then did not return her calls.

Know the news with the 7NEWS app: Download today

She was initially unsure whether Breen had decided to disappear of his own accord, which police now deem unlikely.

His disappearance is now being treated as suspicious and likely the result of foul play.

The change in beliefs came when Breen did not appear at his daughter’s funeral in October 2018, despite his family saying the pair were close.

“His bank accounts and phone have never been accessed and there has never been any reported sightings of Brendan,” police said.

Police have reappealed for information on the 14-year-long missing persons case of Brendan Breen who was last seen aged 55. Credit: Victoria Police

Breen was known to police and had previously spent several years in a correctional facility on fraud charges.

“There are a number of aspects about his disappearance that continue to give us cause for concern, especially the length of time he has been missing with no trace whatsoever,” Detective Inspector Dave Dunstan said.

“We know he had a number of associates who were also known to police and, while they have been spoken to over the years, this remains an active avenue of enquiry for investigators.

“While 14 years have passed, we strongly believe there are still people out there who know what has happened to Brendan, who is involved and why this has happened.”

He also goes by Brendan Green, Brian Green or Brendan Lacombe and is described as 183cm tall with a medium build, olive complexion, grey receding hair and blue eyes.

Anyone with any information regarding Breen’s disappearance is urged to contact Crime Stoppers.

“Even the smallest detail could be what leads us to a breakthrough and hopefully, puts us in a position to give Brendan’s family some answers,” Dunstan said.