Only council-vetted "play rangers" are now allowed to monitor youngsters in two adventure areas in Watford while parents must watch from outside a perimeter fence.
The Watford Borough Council policy has been attacked as insulting and a disgrace by furious relatives who say they are being labelled as potential paedophiles.
It will further fuel concerns over a growing nanny state amid the deepening row over the Government's new national anti-paedophile database.
That will see at least 11 million adults have to be vetted to work with children or vulnerable adults, including parents who give officials lifts to and from social or sports clubs.
Councillors in Watford claim they are only following Government guidelines and cannot allow adults to walk around playgrounds "unchecked".
But Osfted dismissed the ban while parents branded it "a joke".
The rules have been imposed at Harwoods and Harebreaks adventure recreation grounds.
Activities on the half acre sites include a skateboard half-pipe, a zip line, rope swings, den building, arts and crafts, plus a wide range of indoor and outdoor sports activities.
Play rangers currently patrol both parks – which are specifically for children aged five to 15 – and are fully qualified and have been cleared by the Criminal Records Bureau.
Parents already have to 'register' their child on arrival at the free playgrounds so staff have their contact details in the event of an accident.
But now only those who have been CRB vetted by the council can enter the sites, which are surrounded by six foot high steel and wooden fences.
Mother-of-five Marcella Bergin, 35, has been visiting with her three eldest children, Christy, 15, Seamus, 12, and Chloe, 11, for many years without any problems.
She said: "It's like they are branding all parents potential paedophiles which is disgraceful – 99 per cent of people are great parents and certainly not child abusers.
"The whole thing is just a joke and I will certainly not be adhering to the new rules which frankly are crazy."
Mo Mills, 62, a retired youth worker who has six grandchildren, added: "This is typical of the nanny state and I am furious – the council should hang their head in shame at this political correctness gone mad."
Mum-of-eight Jenny Abbasi, 41, said: "I find it insulting that the council are essentially branding everyone paedophiles and telling us we cannot be trusted with our own kids – it's a disgrace."
Claude Knights, the founder of children's charity Kidscape, said the council were "using a sledgehammer to crack nuts".
"They are encouraging a climate where parents and children are rendered suspicious without any proof of wrong doing or guilt," she said.
"Caring parents should not be viewed as a threat and if you are a bona fide parent or carer you are in a better position to look after your children than council staff."
A council notice to parents explains that: "Safeguarding the children and young people who use the site is one of our top priorities.
"Due to Ofsted regulations we have a responsibility to ensure that every authorised adult who enters our site is properly vetted and given a Criminal Records Bureau (CRB) check by Watford Borough Council."
Council Mayor Dorothy Thornhill argued they are merely enforcing government policy at the play areas, in Vicarage Road and Leggatts Way.
She said: "Sadly, in today's climate, you can't have adults walking around unchecked in a children's playground and the adventure playground is not a meeting place for adults.
"We have reviewed our procedures, so although previously some parents have stayed with their children at the discretion of our play workers, this is not something we can continue to do.
"There are other places in the town for parents with small children to go."
But a spokeswoman for Ofsted said: "Ofsted would never seek to prevent parents and carers having access to their own children.
"We would not insist that each parent must have a member of staff with them all times.
"Many settings operate very well with parents and carers present, and indeed this can be an important part of young children settling somewhere new."
The Daily Telegraph disclosed on Tuesday how employers will come under pressure to register staff with the Government's anti-paedophile database even if they have little contact with children
Sir Roger Singleton, the chairman of the Independent Safeguarding Authority, said the scope of the planned database could increase significantly because companies would fear losing business if they did not have their employees vetted.
Last month, he was asked by the Government to look again at the complex definitions of "frequent" and "intensive" contact following concerns that the scheme would lead to state supervision of all relationships between adults and children.
