Hundreds of thousands of mothers are being discharged from hospital too early because of a chronic shortage of midwives, a new report warns.
Research by the Royal College of Midwives (RCM) found that 40% of new mums are told to leave their ward before they are ready, endangering them and their newborn baby.
Experts warned mothers are being "let down by the NHS" and lives are being put at risk - and called for immediate investment to appoint more midwives.
The report also warned that local hospitals are failing to give women the level of care recommended by NHS watchdog, the National Institute for Health and Clinical Excellence (Nice).
And two-thirds of midwives said organisational pressures in the over-stretched NHS is the biggest factor when determining the level of care mothers receive.
While less than a quarter, just 23%, said the needs of the women is the main driving force behind the care.
Jane Munro, the report's author and the Quality and Audit Development Advisor at the RCM, warned that "this report shows us that mothers are being let down by the NHS".
She said mothers are being discharged early and not being given enough advice about how to spot danger signs in their and their baby's health - meaning there could be a delay in diagnosing serious illnesses.
"It could mean that illnesses are not picked up quickly enough, or it could even put lives in danger", she said.
"The shortage of midwives is a continual issue. There has been a commitment to have more midwives, but we still have yet to see them on the ground. There is a severe shortage across the NHS.
"At the moment organisational pressures drive care, and that is quite disappointing. Nice clearly states that discussion should happen with mothers, and that is clearly not happening.
"The midwives just don't have the time. They are just so overstretched they are run off their feet."
She said local NHS commissioners are "failing" to provide the care they should to mums.
The report, entitled Postnatal Care Planning, surveyed more than 3,000 midwives and student midwives and nearly 500 mothers about the care they received.
According to the Office of National Statistics, there were 729,674 live births in England and Wales in 2012, meaning that hundreds of thousands of women each year are potentially sent home from hospital too early.
One of the women surveyed, who remains anonymous, painted a picture of an impersonal maternity service under strain.
She said: "I saw so many different midwives, both before and after the birth of my baby, they had not a hope of offering the kind of care that I wanted. I never had a chance to get to know and trust any of them, and they never had a chance to get to know me".
Cathy Warwick, chief executive of the RCM, said: "The impact good postnatal care has on women's experiences and their long-term health should not be underestimated.
"Postnatal care should always be based on women's needs and not on funding or organisational issues. This reinforces the need for more midwives.
"Numbers have been increasing but not fast enough and England remains seriously short of the numbers needed if care is to be of high quality throughout antenatal, labour and postnatal care. The bottom line is that care must be based on clinical need."
And she warned that without adequate support women and babies are more likely to be readmitted to hospital - costing the NHS and the taxpayer more in the long-run.
The report, the fourth in a five-part series looking at postnatal care, calls for more midwives, and for the number of midwife visits to be based on a woman's need - not financial considerations.