Police investigating the disappearance of Malcolm Levesconte are considering that he may have jumped off the ferry on the way to France.
Mr Levesconte, 59, landlord of the Royal Oak Pub, was last seen at the pub on Sunday, December 9.
Detectives have been able to confirm that Mr Levesconte booked a return ferry ticket to St Malo in France that same evening and boarded a ferry at Portsmouth.
Since then police have been working with the relevant agencies in France to try to trace him but have not been able to confirm if Mr Levesconte actually got off the ferry in St Malo.
Due to evidence that has come to light during their enquiries they have become increasingly concerned for Mr Levesconte’s safety and are now considering the possibility that he jumped off the ferry.
Det Sgt Standing, of Salisbury CID, said: “We continue to treat Malcolm Levesconte’s disappearance as a missing person enquiry but at this stage we do have to accept there is a possibility that he did not make it to France and may have taken his own life by jumping into the sea from the ferry.
“I would like to appeal to anyone who has information to come and speak to us – his family are facing the terrible prospect that he may have committed suicide.
"It is therefore imperative that we hear from you if you have heard from Mr Levesconte.”
In addition, Wiltshire Police are writing to the 61 people believed to have contributed to the Royal Oak pub’s Christmas thrift club in Shrewton which went missing at the same time as Mr Levesconte’s disappearance.
Officers launched an investigation after they were informed of the theft of a substantial amount of money by a member of the public.
Enquiries have established that the £29,000 Christmas thrift fund has disappeared.
The Royal Oak pub remains closed and the family of Mr Levesconte continue to request that the media respect their privacy.
Anyone with information about the whereabouts of Mr Levesconte is asked to contact Salisbury CID on 101, or Crimestoppers on 0800 555 111, where information can be left anonymously.