Many trusts are still placing patients in mixed-sex accommodation, figures from the Conservative Party reveal.
Freedom of Information responses show that 16 per cent of acute trusts and 8 per cent of mental health trusts are using curtains to segregate men and women.
One in seven hospitals and 2 per cent of mental health trusts treat patients in large, dormitory-style accommodation known as Nightingale wards.
NHS Confederation policy director Nigel Edwards said managers had many competing priorities, such as admitting more patients and improving efficiency.
The cost of eliminating mixed-sex wards was more than the£1.5bn identified by the Conservatives, and in some cases would involve knocking down entire buildings and starting from scratch, he said.
Government guidance states patients should not have to walk past bays for members of the opposite sex to get to the toilet or bathroom, and there should be separate facilities.
A third of hospital trusts and nearly a quarter of mental health trusts do not provide segregated toilet facilities for all patients, according to the figures, which cover 132 acute trusts and 55 mental health trusts in England.
There were 6,485 recorded breaches of procedures for segregating patients by sex in hospital trusts and 30 in mental health trusts, although many trusts did not collect this information.
In 2001, New Labour promised in its manifesto to abolish mixed-sex wards.
Health secretary Alan Johnson said last January that the government was committed to "reducing" mixed-sex accommodation.
A year ago, a Department of Health spokesman confirmed to HSJ that the government is "not promising a return to wholly single-sex wards".
Shadow health secretary Andrew Lansley said: "Patients have enough to worry about when they go into hospital without having to suffer the indignity of being placed in accommodation that affords them too little privacy at such a sensitive time.
"Despite hearing Labour ministers make promise after promise to end the scandal of mixed-sex wards, we have not seen the necessary action and they continue to blight our hospitals."