Health officials have pulled out of publishing recommendations on safe staffing after Health Secretary Jeremy Hunt gave the responsibility to the newly-formed NHS Improvement body.
The National Institute of Health and Care Excellence (Nice) was going to go ahead with publishing them anyway, but announced tonight it would not do so.
Chief executive Andrew Dillon said: "The work on safe staffing will now be taken forward by the newly-formed NHS Improvement, in conjunction with NHS England.
"The conclusions reached by our advisory committee on safe nurse staffing in accident and emergency departments will now become part of a wider review.
"It is important that we do not pre-empt the outcome of the work to be done by NHS Improvement and NHS England by publishing our conclusions at this stage. However, we do understand and welcome the public interest in our review of the evidence on safe staffing.
"With this in mind, the Department of Health have confirmed that NHS Improvement will publish our final recommendations later this year, as part of the evidence base for the safe staffing guidelines they are now developing.
"Nice stands ready to support this work using the experience we have gained over the last two years."
Mr Hunt announced the creation of NHS Improvement earlier this month as part of a series of measures to improve patient safety.
Safe staffing guidance was deemed necessary following the Francis report, which stated that inadequate staffing levels at Mid Staffordshire resulted in poor quality of care, leading to hundreds of deaths in the 2000s.
Eddie Jones, head of the clinical negligence department at JMW Solicitors, said the decision by Nice not to issue its safe staffing guidelines was "a matter of concern".
He added: "Having previously made clear its intention to publish this information, it would appear to have come under pressure not to do so.
"That can only undermine confidence and the prospect of this material coming to light.
"My concern is whether this is an indication of how Nice is to be treated by this Government.
"It has been regarded as independent of the Department of Health and yet this episode seems to be an example of Government wanting to bring matters in house in order to reduce criticism of the NHS.
"By doing so, that might limit the effective scrutiny of the NHS which Nice has provided."