Jonathan Jones, 37, of Orpington, Kent, was freed on 25 April after the three Appeal Court judges said they were all "of the clear view" that his conviction for killing Harry Tooze, 64, and his 67-year-old wife Megan were unsafe.
Yesterday he urged police to follow up "a whole host of leads" mentioned by the Court of Appeal judges in their reasons for freeing him.
Mr Jones and his girlfriend Cheryl Tooze were outraged when South Wales police issued a statement, shortly afterwards, saying they were not looking for anyone else in connection with the killings at the Toozes' farmhouse in Llanharry, Mid Glamorgan, in July, 1993.
But yesterday, in their reasons for clearing Mr Jones, the judges mentioned sightings of four-wheel drive vehicles near the farmhouse, noisy arguments and a mystery middle-aged man seen with the Toozes.
Mr Jones said: "It is now time the police got off their backsides and reopened the investigation. I know they have been investigating the case even while I was in prison and it is no good from them to say that they are waiting for new evidence.
"The judges mentioned a whole host of leads which were never followed up. The police own computers which could have been used to try to trace the Suzuki seen near the farmhouse by neighbours. That was never done."
He added: "I don't think the inquiry was ever completed. It was superficial. It should not just be closed, it should be reopened and lessons learnt from what has happened."
Ms Tooze, 36, said: "I no longer have any respect for the South Wales police . . . Somewhere there is a person or persons who killed my parents out there and they may kill again. That is why the investigation must be reopened but I don't think South Wales police should do it."
South Wales police later stressed that the file on the murders was not closed. Assistant Chief Constable Bob Evans said: "We wish to re-emphasise that we will rigorously follow up any new information which may come to light in respect of these murders."