The lives of new mothers and babies are at risk from poor conditions on maternity wards, the health watchdog has warned.
Chronic staff and equipment shortages make giving birth more dangerous than necessary, the Healthcare Commission found.
An investigation found poor organisation on wards, doctors who do not explain what is happening to patients, and dirty toilets as well as a shortage of midwives. Bad management rather than a lack of money that is at the root of the problems, says the Commission report to MPs.
The situation is so bad that chairman Sir Ian Kennedy decided to highlight the concerns over maternity care ahead of publication of the broader report on the NHS to MPs today.
That will focus for the first time on patients' experience of the National Health Service.
Speaking ahead of the launch, Sir Ian called on all trusts to review their maternity services because of huge differences between the best and worst.
It is the first time he has issued such a strongly-worded warning about the state of NHS practices since the commission was set up two years ago.
"Our work has shown that these is too much poor practice that needs to be rooted out," Sir Ian said.
"Giving birth is probably safer now, in overall terms, than it ever was and there are lots of examples of good practice.
"However, this is an area where the consequences of things going wrong are very great.
"And there is growing evidence that in some places maternity services are not as good or safe as they should be."
The commission examined conditions at three maternity units - including one in the Midlands - that have suffered high mortality rates over the past two years.
One of the worst was at Northwick Park in north London where ten women died during or after birth.
However, common themes emerged during the course of the investigation, according to the commission.
At New Cross Hospital, Wolverhampton, a review by commission inspectors of 20 deaths between 2001 and 2003 found that half might have lived with better care.
The third investigation, at Ashford and St Peter's NHS Trust in Surrey, did not find evidence of unnecessary deaths but concluded " feuding" between consultants was jeopardising patient care.
Across the health service, Sir Ian fears staff shortages, aged buildings, poor training and weak management are hitting standards.
Health Minister Liam Byrne said: "Sir Ian Kennedy raises some extremely important issues, which we are taking seriously.
"We welcome his acknowledgement that giving birth is safer now than ever before and that very few babies or mothers die.
"However services are not yet good enough to meet the needs of all women and babies, wherever they live and whoever they are, and that is why the Government continues in reforming, as well as investing in, maternity services in the UK. This week we are bringing together the best brains in maternity to launch our action plan for world class maternity services."
Shadow health secretary Andrew Lansley said: "These findings show that despite increasing resources for the NHS, a lack of genuine reform means resources are wasted and services are not held accountable for the standards they meet."