Aim. This study explored the opinions of nurses and doctors working in emergency departments towards the development of the Acute Care Nurse Practitioner service in the United Kingdom. Background. Studies carried out in the United States and Canada suggest that the Acute Care Nurse Practitioner can have a positive impact on the critically ill or injured patients' experiences in the emergency department. This role is well developed in the United States and Canada, but is still in its infancy in the United Kingdom. Design and methods. A descriptive, exploratory design incorporating questionnaires (n = 98) and semi-structured interviews (n = 6) was employed. The sample included nurses and doctors from seven emergency departments and minor injury units. Results. Respondents felt it was important for the Acute Care Nurse Practitioner to have obtained a specialist nurse practitioner qualification and that the Acute Care Nurse Practitioner should retain a clinical remit. While participants seemed comfortable with nurses undertaking traditional advanced skills such as suturing, reluctance was displayed with other advanced skills such as needle thoracocentesis. Three main themes were identified from the interviews: inter-professional conflict, autonomy and the need for the Acute Care Nurse Practitioner. Discussion. Doctors were reluctant to allow nurses to practise certain additional advanced skills and difficulties appear to be centred on the autonomy and other associated inter-professional conflicts with the role of the Acute Care Nurse Practitioner. Conclusion. Nurses and doctors identified a need for the Acute Care Nurse Practitioner, but the blurring of boundaries between doctors and nurses can result in inter-professional conflict unless this is addressed prior to the introduction of such advanced practitioners. Relevance to clinical practice. As the role of the emergency nurse diversifies and expands, this study re-affirms the importance of inter-professional collaboration when seeking approval for role expansions in nursing.