By Imogen Willcocks
Every day, over a million working parents use childminders and private nurseries, believing their babies are in hands of highly qualified, strictly regulated and genuine caring people.
Terrifyingly, many of them are wrong.
Last year an inspector at Ofsted - the government agency that regulates childminders and nurseries - phoned the BBC Whistleblower programme and told me a chilling story.
Out of 700 nurseries she and colleagues had inspected, she had found only five that she would have let her own two children go to.
She told me that Ofsted inspection reports - the only thing parents have to go on when choosing a nursery - aren't worth the paper they're printed on.
"We are literally skimming the surface", my Ofsted whistleblower said. "We are told constantly: 'if you don't see a problem, don't look for one. Take a quick look and get out'.
"The number one priority for all Ofsted inspectors is to meet their targets. Because if they don't they are disciplined. Targets take priority over safeguarding children," she said.
I decided to test her claims by going undercover and getting myself a job in a number of nurseries.
At first I thought there might be a problem. I was 21. I have never had any children and apart from a couple of babysitting stints, have no experience looking after babies and toddlers.
I needn't have worried. None of the nurseries I worked for bothered to check my fake CV or fictitious references and even Ofsted itself, who at least checked my criminal record, registered me as a child-minder, even though the premises were totally unsuitable.
We'd had a tip-off about the Buttons nursery in Hanwell, west London, saying its supervision of babies and toddlers was unacceptable.
After a cursory interview I was appointed as a nursery assistant.
No one checked my references and in the five weeks I was there, they never received the all clear from the Criminal Records Bureau (CRB). I could have been anyone.
Buttons is based in a rambling, 19th Century detached house and caters to the area's professional middle classes.
It was not cheap, charging £1,100 a month for a child under two.
For that kind of money parents get to drop off their babies and toddlers at 8am and pick them up at 6pm.
I was terrified, partly because of the fear that my secret filming equipment would be discovered, but mostly because apart from a quick nappy-changing lesson with a friend's baby, I had no idea how to look after children.
No one noticed my inexperience. At 21, I was actually one of the oldest nursery assistants there.
Many of them were trainees and had no idea what they were supposed to be doing. There was no on-the-job training.
Instead you were thrown in at the deep end. At times I was on my own with as many as 13 children - although the law says carers waiting for their CRB clearance should always be closely supervised at all times.
And they should not be allowed to change nappies and take children to the toilet.
With that many children to look after, I could barely make sure they were safe, let alone care for them individually.
Instead it was just damage limitation - I found myself grabbing broken glass, sticks and sharp objects from children as young as three.
One day builders were brought in to fit guards to the radiators because one little boy - weeks earlier - had badly burnt his hand on one.
The other staff told me that the owner, Satnam Parhar, had blamed the staff for not supervising him properly.
They said he was only getting the guards fitted because an Ofsted inspection was due.
While the builders were there, they left their power tools inches away from where the children were playing and no-one seemed to notice.
Along with the other nursery assistants at Buttons, I was poorly supervised and very poorly paid.
I was on about £100 a week - nearly less than half the legal minimum wage. It's hardly surprising, then, that many of the staff were less than high-quality carers.
I saw two nursery assistants hauling a boy across the nursery by his arm. Then heard a child being called a "shit-bag", and saw a little girl's head being shoved into the mattress because she didn't want to go to sleep.
When I complained to Mr Parhar that I had been left on my own with 13 children, he refused to accept what I was saying and called the idea crazy.
When I contacted him about what I'd be reporting for BBC One's Whistleblower programme, he issued a statement saying: "Buttons day nursery is a family run nursery with a loyal following.
"The care and safety of our children is of utmost importance. Buttons has regularly received favourable Ofsted reports one as recently as February 2008.
"New joiners undertake a full induction programme and there are procedures in place to ensure the safety of children.
We take any allegations or criticism very seriously and will investigate these complaints and take appropriate action."
My eight-month investigation in various establishments had uncovered a childcare culture where a new carer's criminal records and references are never checked, yet they will immediately be left alone with young, vulnerable children.
Ofsted said in a statement that it would consider making improvements based on the things I had uncovered.
But it added: "Ours is the most intensive inspection and monitoring system in Europe.
"Our inspections of nurseries and childminders are rigorous and the vast majority of our inspectors are highly skilled professionals who do a good job.
"Our policy of unannounced inspections keeps most nurseries and childminders on their toes."
I don't yet have children. When I finished my undercover work I could return to normal without worrying about where to put my children.
But now I worry about the children of my friends. And having seen what I've seen, I can't imagine I'll ever have my own babies and put them into childcare.
Whistleblower is on BBC One at 2000 GMT, Wednesday, 5 March