Mr Lubbock, 31, was found dead in the TV presenter’s pool in Roydon, Essex, in March 2001 following a party.
The unnamed suspect, aged 50, was arrested in Cheshire on 17 March following “significant new information”, Essex Police said.
He was then given bail until 12 April.
But on Sunday Essex Police said: “A 50-year-old man arrested on suspicion of the indecent assault and murder of Stuart Lubbock has been released under investigation while our enquiries continue.”
Last month Det Supt Lucy Morris said the investigation had been “extremely lengthy and complex”.
“We have never given up on finding out what exactly happened to Stuart and we will not stop in our pursuit of justice for him and for his family and friends,” Det Supt Morris said.
Mr Lubbock, a butcher from Harlow, was described by neighbours at the time of his death as a “pleasant, sociable” man.
A post-mortem examination found Mr Lubbock had suffered “horrific” injuries prior to his death, police said.