Almost 60% of nurses say their wards are "dangerously understaffed" all or some of the time, according to a snapshot survey.
The poll of 526 nurses for Nursing Times magazine found 57% believed their wards were dangerous due to too few staff.
A year after Robert Francis QC published his report into failings at Stafford Hospital, where hundreds of people died needlessly contributed to by neglect, 39% of nurses said staffing levels had worsened where they work over the last 12 months.
Some 37% said they have stayed the same while only 22% reported an improvement.
Last year, the Nursing Times survey found the same percentage of nurses saying their wards were dangerously understaffed.
A third (33%) of those questioned in the new poll said patient safety had got worse over the past 12 months, 19% thought it was better and 48% said there had been "no change".
Two-thirds - 65% -said they had witnessed "poor care" in their ward or unit over recent months, down from 76% in last year's survey.
Meanwhile, 42% of nurses thought the Francis report would improve things in the long term for the NHS and nursing, 28% said it would make no difference and 24% felt it had led to unfair criticism of the profession and the NHS.
Nursing Times editor, Jenni Middleton, said: "Francis confirmed what many in the profession have always known - that without the correct number of staff to deliver care, patients will be being put at risk.
"Our survey shows that nurses are still witnessing poor care far too much, and that they believe their wards are dangerous because they have too few staff. It is time to act on that information, and put patients first by having the right amount of nurses to look after them - at all times."
One nurse told the magazine: "Although my organisation has been recruiting more nursing staff they have been inexperienced and have had to be supervised, so in some cases have made matters harder."
Another said: "There just aren't the number of nurses out there to recruit and I believe this will only get worse."
Shadow health minister, Jamie Reed, said: "These figures make a mockery of everything the Government has tried to claim in the last year. Too many nurses can see things are heading in the wrong direction.
"In the response to Francis, the Government stopped short of requiring action on staffing levels. By presiding over the loss of thousands of NHS nurses, the Government is making care failures more likely, not less.
"For three years we told ministers that nurse numbers were falling, but David Cameron ignored the warnings.
"This winter he's left the NHS facing an A&E crisis with thousands fewer nurses. It is yet more proof that you can't trust the Tories with the NHS."
In November, the Government's response to the inquiry into Stafford Hospital stopped short of introducing a minimum staff-patient ratio on wards or enshrining this in law.
Organisations including the Royal College of Nursing (RCN) have called for a minimum of one nurse for every eight patients and Australia and parts of the US have a legal staff-to-patient minimum ratio.
Health Secretary, Jeremy Hunt, said the Government would not introduce a legal minimum because staff requirements were a "different number for different wards".
He said forcing hospitals to publish monthly data on ward staffing would be a "huge step" forward, adding that some of the problems at Mid Staffs would have come to light with greater transparency.
The inquiry into the scandal at Mid Staffordshire NHS Foundation Trust, where between 400 and 1,200 more patients died than would normally be expected, put forward 290 recommendations on improving care in English hospitals.
Mr Francis identified a culture where patients were not at the heart of the system and said failings went from the top to the bottom of the NHS.
Figures from the Health and Social Care Information Centre (HSCIC) in January showed a rise in the number of nurses working in hospitals under the acute, general and elderly category since the Francis report, with most of the increase attributable to first level (more junior) nurses.
There has been a drop in the number of other types of nurses, including community nurses, those for people with mental health problems and learning disabilities, community services and those working in schools.
A Department of Health spokesman said more nurses were now working in the the acute, general and elderly category.
He said: "NHS hospitals hired 2,400 more nurses in just 10 months after the Francis report. That means there are over 3,300 more nurses working on NHS hospital wards since May 2010. The Francis effect is well under way - real change is happening and care is being put right back at the heart of everything the NHS does.
"Our plans mean that, for the first time, we will know how many doctors and nurses we need and how many we have, ward by ward. And if hospitals do not have enough, the chief inspector will step in and take action. This is a huge step forward for patients."