The National Childbirth Trust (NCT) says care and support for women in the first days after giving birth is hugely important.
But an NCT survey has found many women do not get the help they so badly need.
Six out of 10 women in the UK said there were not enough midwives available to care for them in the first days after giving birth.
A quarter did not think staff had been kind or understanding and half said they had needed more emotional support from nurses and professionals in the first three days of motherhood.
Women complained of dirty maternity wards and of having to clean bathrooms themselves before they could wash.
Staff overworked
They said staff were so overworked they did not have time to help women with feeding or caring for their new babies.
The survey asked women about three periods of time following labour: the first three days after giving birth; between four and 10 days later and 11-30 days after that.
One in five women said they received less emotional support than they needed after the first four days motherhood.
Half said they wanted more information and support as they tried to cope with their new baby.
In the last period, 50% of the women said they were still not receiving enough information, advice and care.
One in six said they had received no help as their babies neared a month old.
Chief executive of the National Childbirth Trust, Belinda Phipps, said: "Public health is in danger and without backing from the health services for mothers this will simply store up trouble for the future.
"This is a clear example of the NHS failing new mothers, many of whom, without support from either family or the NHS, may suffer mental or physical health problems and may find it difficult to give their babies the care and attention they need."
A spokesman for the Royal College of Midwives said much of the problem was due a shortage of midwives working in the NHS.
He called on the government to improve pay and conditions to attract more people into the profession.
He said: "If we had more midwives that would allow the opportunity for much more one to one care.
"This survey demonstrates that where women receive one to one care their emotional and practical needs can be satisfied in the crucial immediate post-natal period."