A 16-year-old girl in the
care of Somerset County Council is alleged to have had a sexual
relationship with a member of children's services staff.
The council was sent an anonymous letter about the relationship in January, BBC Somerset has discovered.The letter also described a failure by management to respond to staff concerns about it.
An independent investigation found, on the balance of probability, most of the allegations were based in fact.
Earlier this month the council was summoned to a meeting with the government over wider ongoing failings in its children's services department.
In response to the latest development, a council spokesman said it had commissioned its own report into safeguarding which had "raised considerable concerns for us".
'Inappropriate sexual boundaries' The external company which carried out the investigation, in response to the anonymous letter, reported back at the start of August and the conclusions have been seen by the BBC.
It found there had been a significant failure in safeguarding the welfare of at least one young person in care and described "inappropriate sexual boundaries" modelled by a manager.
It is understood the male staff member allegedly involved in the relationship quit his job before the independent investigation, and is now living with the girl who has recently had a baby.
Avon and Somerset Police said: "A formal police investigation into an allegation of abuse of position of trust has now started, but is at an early stage and no arrests have been made."
The force said it originally received an anonymous call about the allegations in September last year.
Officers could not get hold of the caller again so came up with a strategy, along with children's social care and the Local Authority Designated Officer who investigates such reports.
'Placed on leave' The teenage girl who is alleged to have been in the relationship was interviewed and denied any relationship, the police could not find any evidence and charges were not brought.
A council spokesman said: "Allegations were made about an unnamed member of staff in an anonymous phone call on 15 October 2013.
"Normal safeguarding procedures were followed and the matter was formally discussed with the police's Safeguarding Co-ordination Unit on the same day.
"A further contact identified the member of staff five days later and he was immediately placed on leave.
"He then left the authority without working another shift for the authority.
"Since then we have commissioned our own report into safeguarding and it raised considerable concerns for us.
"Somerset County Council has invested heavily in its children's services.
"Vulnerable young people in our care or who have recently been in our care are a priority for this authority."