More than half of nurses surveyed said they did not have enough time
Four out of 10 nurses say staff shortages compromise patient care at least once a week, according to the Royal College of Nurses.
An RCN manifesto to all the political parties says NHS employers must assure themselves they have safe staff levels.
The RCN, whose survey covers the views of 9,000 nurses, is warning against job cuts due to possible reduced funding.
NHS trusts said managers were increasingly examining their workforces to best use the skills of their staff.
THE RCN MANIFESTO
Stand up for staff who speak out
Safer staffing levels
Give nurses time to train
Regulate the drinks industry
Improve care for long-term conditions
Current levels of health spending should be maintained
The RCN has issued its 2009 Employment Survey which covers the views of 9,000 nurses.
It shows that more than half (55%) say they are too busy to provide the level of care they would like.
Almost two thirds (67%) consider their workload is too heavy.
And nurses say they are looking after more patients on the wards.
Dr Peter Carter, head of the RCN, said staff were concerned that they were delivering the basics but were unable to provide the full range of quality care they would like.
He said: "Nurses and healthcare assistants feel up against it, worn down and exhausted by the pressure to make efficiencies and frustrated by being prevented from delivering the quality of care they want to be providing."
The RCN are also warning of a shortfall in the number of nurses in coming years.
The RCN's Labour Market Review said about 200,000 nurses are expected to retire in the next 10 years, there will be fewer newly qualified nurses and fewer nurses moving to the UK because of restrictions on migration.
The RCN says the impact of growing retirements from the profession will be felt first in the community sector where most of the nurses tend to be older.
Dr Carter said: "The nursing workforce has grown in recent years but only just enough to keep up with rising demands on healthcare.
"We expect the next few years will be the most challenging for staff levels in decades.
"There is considerable pressure to focus on short-term funding constraints and cut staff numbers without taking patient needs into consideration.
"Policy makers must look at the workforce in conjunction with their ability to deliver high quality and safe care."
Karen Charman, head of employment services at NHS Employers which represents trusts in England, said NHS organisations certainly needed to have a clear method of working out safe staffing levels in order that patient care was not harmed.
"There are a number of different ways of achieving this and we believe that this should be determined at local level," she said.
"Advice from professional bodies is extremely important to help trusts ensure that clinical standards and staffing levels are right to ensure the safety of patients.
"However, fixed staffing ratios do not provide the flexibility to meet differing local circumstances and care settings
"Employers are increasingly examining the different roles within their workforce to best use the skills of their staff."