A senior detective is being investigated for "misconduct", Wiltshire Police has confirmed.
It said Supt Sean Memory, who is investigating claims of historical child abuse against the late Sir Edward Heath, is off work "through sickness".
But it added the probe did not relate to Operation Conifer or his work as the senior investigating officer.
The Sir Edward Heath Charitable Foundation is confident the former Tory prime minister's name would be cleared.
The force issued the statement following "a number of approaches from the media" regarding Operation Conifer.
Supt Steve Kirby will become the lead officer in the investigation in Mr Memory's place, Wiltshire Police said.
The force said the investigation against Mr Memory "is not an indication of guilt" but "a process which has to be followed as laid out in the Police Regulations".
It also confirmed the "conduct under investigation" does not warrant suspension, "therefore Supt Memory is not suspended from duty".
Operation Conifer began in 2015 after claims were raised in an inquiry by the Independent Police Complaints Commission (IPCC).
Information from a retired officer had sparked concerns that Wiltshire Police had deliberately caused a criminal prosecution against a suspected brothel keeper to fail in 1994.
Last year the IPCC said it had found no evidence that the case was dropped because the woman threatened to make allegations against Sir Edward.
But Wiltshire Police has said Operation Conifer is also investigating a number of separate allegations made by persons who came forward. It said the inquiry additionally aims to safeguard children and vulnerable adults who may be at risk of abuse today.
Mr Heath died at home in Salisbury in July 2005, aged 89.