Local NHS ads have been banned for the "misleading and potentially harmful" claim that A&E is for life-threatening emergencies only.
The poster and claims on the NHS Brent Clinical Commissioning Group (BCCG)-run rightcare4u.org.uk website said: "A&E is for life-threatening emergencies only ... Other NHS services are available that will help you more quickly."
The website also said: "If you use A&E when you could get help somewhere else, you are taking NHS staff time away from life-threatening cases. Other NHS services are available that will help you more quickly."
Brent Patient Voice complained that the claim was misleading and potentially harmful because it could discourage patients with serious medical conditions or injuries that were not necessarily life-threatening from going to their nearest hospital A&E.
The BCCG, which is responsible for planning and buying many of the health services needed by the 325,000 people who live in Brent, said the ads focused on diverting unnecessary cases away from local A&E departments to more appropriate settings such as urgent care centres and minor injuries units, and their primary aim was patient safety.
There were well-established protocols in place in order to safely refer all patients needing A&E treatment who presented at urgent care centres, it said.
The Advertising Standards Authority (ASA) understood that there were certain medical conditions and injuries such as some broken bones, facial injuries requiring maxillofacial surgery and serious eye injuries that were not life-threatening but needed A&E treatment.
It said: "We acknowledged that the intention behind the ad campaign was to encourage the appropriate use of A&E services, so as to ensure the proper allocation of NHS resources and patient safety, and was not to deter individuals from accessing A&E services if they genuinely required them.
"However, we noted that the claim 'A&E is for life-threatening emergencies only' was an absolute claim, even though there were exceptions, and we were concerned that individuals presenting with the conditions listed above might be deterred from seeking urgent treatment at A&E as a result of seeing the ads."
Brent Patient Voice said it tried several times but failed to get the BCCG to withdraw the ads.
The group's chairman, Robin Sharp, said: "It is vital that ads like these should be truthful. We regret that we had to take it so far, because we remain keen to work with NHS colleagues to improve services for the people of Brent."
A BCCG spokesman said: "The ASA acknowledges that the intention behind our advertising campaign was to help support A&E staff to treat the most urgent cases as quickly as possible. Its ruling is based on a single complaint out of a total patient population of nearly one million.
"The campaign had the support of local hospitals and doctors, given that many people often use A&E for minor ailments, adding additional pressure onto staff who are there to treat more serious cases.
"Our objective was to communicate clearly to our local population about the role of A&E services and to highlight alternative options where appropriate.
"This helps individuals to get the right care in the right place and supports those patients who genuinely require urgent and life-threatening A&E treatment."