Social workers set up a CCTV camera in the bedroom of a couple with learning difficulties in order to monitor their behaviour, a new report claims.
Council staff are said to have spied on the young parents at night as part of a plan to see if they were fit to look after their baby, who was sleeping in another room.
The mother and father were forced to cite the Human Rights Act, which protects the right to a private life, before the social services team backed down and agreed to switch off the surveillance camera while they were in bed together.
The case is highlighted in a new dossier of human rights abuses carried out against vulnerable and elderly adults in nursing homes and hospitals across Britain.
It comes just days after the Government admitted town halls have gone too far in using anti-terror laws to snoop on members of the public.
Recent figures show three-quarters of local authorities have used powers granted under the Regulation of Investigatory Powers Act to spy on residents suspected of putting their bins out on the wrong day, allowing pet dogs to foul the pavement or breaking school catchment area rules.
In the latest case, documented in a report published by the British Institute of Human Rights to mark the tenth anniversary of the Human Rights Act, an unnamed council used CCTV to keep an eye on a mother and father with learning difficulties as their parenting skills were under question.
Social services departments are allowed to place adults in units known as "residential family centres" if they fear their children could be at risk of abuse or neglect. Staff assess the families in a controlled environment to determine whether their children should be taken into care.
The centres can use CCTV cameras as well as listening devices but Government regulations state that staff must "respect parents' and children's privacy".
However, the BIHR report claims that the centre in question breached the couple's right to respect for private and family life, enshrined in Article 8 of the European Convention on Human Rights that was incorporated into English law a decade ago.
The study states: "A learning disabled couple were living in a residential assessment centre so their parenting skills could be assessed by the local social services department.
"CCTV cameras were installed, including in their bedroom. Social workers explained that the cameras were there to observe them performing their parental duties and for the protection of their baby.
"The couple were especially distressed by the use of the CCTV cameras in their bedroom during the night.
"With the help of a visiting neighbour, the couple successfully invoked their right to respect for private life.
"They explained that they did not want their intimacy to be monitored and that, besides, the baby slept in a separate nursery.
"As a result, the social services team agreed to switch off the cameras during the night so that the couple could enjoy their evenings together in privacy."
The BIHR said the case illustrated the way in which the much-maligned Act, which has given birth to a new industry of specialist lawyers and led to convicted murderers and terrorists winning the right to remain living in Britain, had also made it easier for innocent people to have their rights protected without the need for costly court cases.
Ceri Goddard, its acting director, said: "The Human Rights Act is 10 years old and should be celebrated for the positive changes it is making to people's everyday lives – in our hospitals, care homes and schools."