Thousands of women are left alone during and shortly after labour, leaving them feeling vulnerable and potentially at risk, a survey shows.
The poll will feed into a wider review into maternity care
A Healthcare Commission poll of 26,000 women found one in four had felt worried when left alone by medics.
Midwives said the findings raised concerns as one-to-one care was key to spotting problems that may arise.
The poll also identified significant variations in care among 148 NHS trusts across England.
In some trusts, one in 10 women said they were left alone at a time that worried them, this compared to a third in some trusts.
The watchdog said the findings suggested midwives were not following official guidelines that women should only be left alone for short periods.
The poll, which will form part of a national review of services to be published next year, also highlighted a number of other issues.
Some 43% of those surveyed also said they were not given a choice of where they gave birth - again in defiance of guidelines.
And 36% of women said they were not offered antenatal classes, while over half of women gave birth lying down - a position midwives are meant to discourage.
A fifth of women also described hospital food a poor.
Louise Silverton, of the Royal College of Midwives, said: "It is a serious concern that too many women are left alone during labour, leaving them feeling worried and vulnerable.
"The main way to solve these problems is simply to improve midwife numbers.
"Without this the government's targets will just be broken promises, and we have seen this too often in the past."
And Mary Newburn, head of policy research at National Childbirth Trust, added one-to-one support improved a woman's "experience and outcomes".
Shadow health minister Anne Milton said the findings revealed "serious problems with the government's maternity strategy".
And Liberal Democrat health spokesman Norman Lamb added: "This survey shows the huge gap between government promises and the reality in maternity units across the country."
Dr Gwyneth Lewis, the government's maternity services expert, said it would help health professionals focus attention on the areas that needed improving.
She added: "It is encouraging that the vast majority of respondents reported their care during labour and birth as being "excellent", "very good" or "good".
"We want to see these positive experiences replicated throughout the entire process."