Lucy Jarrett: "Our children have grown up together"
Ofsted inspectors in England have been told by ministers to show "common sense" in interpreting laws on friends helping each other with childcare.
Two mothers had been told it was illegal to look after each others' children without being registered.
The reciprocal arrangement had been seen as providing a "reward".
A spokesman for the Department for Children, Schools and Families said childcare rules were not intended to "interfere in informal arrangements".
Ministers are trying to clear up confusion over the regulations in England covering parents who help each other with childcare and babysitting.
But so far there is no new guidance on the regulations introduced in 2006 - which appear to require compulsory registration for parents who have a regular after-school arrangement for looking after each others' children.
In Buckinghamshire two mothers, both police officers, were told by children's services watchdog Ofsted that they were breaking the law by caring for each others' children without undergoing registration and checks.
The two detective constables, Leanne Shepherd, from Milton Keynes, and Lucy Jarrett, from Buckingham, told the BBC how Ofsted insisted they end their arrangement.
Ms Shepherd said: "A lady came to the front door and she identified herself as being from Ofsted. She said a complaint had been made that I was illegally childminding.
"I was just shocked - I thought they were a bit confused about the arrangement between us.
"So I invited her in and told her situation - the arrangement between Lucy and I - and I was shocked when she told me I was breaking the law."
The accusation was that the reciprocal arrangement represented a "reward" - and as such the mothers would have to be formally registered as providers of child care.
The Department for Children, Schools and Families has been arguing that this is not how the Childcare Act introduced three years ago should be interpreted.
In particular, it wants a different view of what represents a "reward".
The law makes no distinction between the financial reward gained by someone paid to look after children and the reward in time and convenience gained by families who have private arrangements to help each other with childcare.
"Reward is not just a case of money changing hands. The supply of services or goods and in some circumstances reciprocal arrangements can also constitute reward," says Ofsted.
A spokesman for the children's department said it was now "working with Ofsted on their interpretation of the word 'reward'."
"We must ensure a common sense and measured approach which does not penalise informal arrangements but retains a balance between over-regulation and protecting children."
'Bureaucracy gone mad'
Ofsted only operates in England, so this interpretation of the law on childcare for "reward" applies to England rather than elsewhere in the UK.
Under the complex childcare rules, it is illegal for an unregistered parent to collect someone else's child from school and look after them for more than two hours, if this is a reciprocal arrangement and so providing a "reward".
This would mean that after-school play-dates - where families helped each other by taking home each others' children on different days - would not be permissible without registration and inspections.
There are exemptions for this - allowing relatives to look after children in their family and the restrictions do no apply if children are in their own home or between the hours of 6pm and 2am.
The suggestion that it would be illegal for friends to help each other with childcare has provoked an angry response.
Michele Elliott, director of children's charity Kidscape, said the decision defied common sense and would impose extra childcare costs on families.
She described the rules as "bureaucracy gone mad".
Siobhan Freegard, who founded the parents' networking website Netmums, said that hard-pressed parents would think "this is the last straw".
This dispute over child care regulations follows recent controversy when it emerged that a forthcoming child protection vetting scheme will mean more than 11 million adults in England will have to undergo checks.
There was widespread hostility to the extent of the plan - and Children's Secretary Ed Balls announced a review.
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