Hospitals employing staff ratios of more than eight patients per nurse on a “regular basis” can increase the risk of harm in adult hospital wards, draft government-backed guidelines show.

This warning comes in proposed recommendations on nursing workforce levels in adult inpatient wards in acute hospitals by the National Institute for Health and Care Excellence.

Published this week, they are the first in a series of guidelines on safe staffing in different healthcare settings that NICE was asked to produce by the health secretary as part of the government’s response to the Francis report.

The draft guidelines points to an increased risk of harm when registered nurses are expected to care for more than eight patients during the day time on a regular basis. The proposals stop short of saying trusts should never go below this.

The government has consistently rejected the idea of setting a single minimum staffing level, despite increasing support for a ratio of one nurse for every eight patients on acute wards.

Evidence from the National Nursing Research Unit shows that a ratio of registered nurses to patients below a level of one to eight was associated with higher mortality rates and patient harm.

Gillian Leng, deputy chief executive and director of health and social care at NICE, said: “There is no floor or ceiling number on the required number of nursing staff that can be applied across the whole of the NHS.

“What the [NICE] safe staffing advisory committee concluded was that assessing patient needs was paramount when making decisions about the number of nursing staff and planning should allow for flexibility on a day-to-day or shift-by-shift basis.”

Increasing staffing levels to comply with the guidance could mean some trusts have to make significant extra investment in staffing.

The draft guideline highlights a series of “red-flag events” which should signal that a ward is in danger of becoming understaffed.

Red flag events include patients not being provided with basic care requirements, such as help with visits to the bathroom, being asked about pain levels or delays in providing medicines.

The document also said that providing a higher proportion of registered nurses in the skill mix contributes to better outcomes for patients and called for hospital boards and senior management to take greater responsibility for safe staffing levels.

It includes step-by-step guidance on how to determine the number of nursing staff that should be funded.

Under separate guidance on safe staffing produced by NHS England in the wake of the Francis report trust boards will be required to review staffing levels every six months using a recognised tool and will be expected to take the new NICE guidelines into account.

They will also be expected to display the number of staff on each shift outside all inpatient wards.

To support use of the guideline in hospitals, NICE said it would be assessing a range of practical toolkits designed to assist in estimating staffing requirements. Staffing toolkits which comply with guideline recommendations and meet specified criteria will be given the NICE endorsement.