A row has broken out between a major NHS hospital trust and the regional ambulance service over allegations that patients are being held in parked ambulances outside the hospital rather than admitted to its emergency department, allowing the trust to report that no corridor care takes place on its premises.

The dispute centres on University Hospitals Coventry and Warwickshire NHS Trust, which has recorded zero corridor care patients under NHS England's regulatory framework. Evidence submitted to a regional ambulance service quality governance committee suggests the absence of corridor patients inside the building is, at least in part, a consequence of patients remaining inside ambulances in the car park outside. Because those patients never cross the threshold into the hospital, they do not appear in its internal figures.

The practical effect is that ambulances are being used as static holding spaces for patients who have already arrived at hospital but have not been formally handed over. Paramedic crews cannot leave until the handover is complete, which means vehicles are unavailable to respond to emergency calls elsewhere in the region. Staff representatives from the West Midlands Ambulance Service have told the governance committee that even moving a small number of patients inside the building at any given time would free up multiple crews for active deployment.

Medical leadership at West Midlands Ambulance Service has been direct about what it believes is driving this. NHS England has applied significant pressure on hospital trusts to eliminate corridor care, and that pressure has produced results on paper. What it has also done, ambulance directors argue, is shift the problem outside the building rather than resolve it. Handover delays attract considerably less regulatory scrutiny than corridor care, which means trusts can tolerate long external queues without the same institutional consequences they would face for visible overcrowding inside.

The concern is not simply about metrics. Ambulances queuing outside a hospital are ambulances not responding to 999 calls. The longer a crew waits for a handover, the longer someone elsewhere in Coventry or the wider West Midlands waits for an emergency response. Frontline staff have described the situation as a gridlock that benefits no one except the trust's performance record.

University Hospitals Coventry and Warwickshire has rejected the characterisation of its practices as manipulative. The trust says it does not use corridor care because it has created designated escalation spaces within its existing ward and bay infrastructure to absorb surges in patient demand. On that basis, it argues, the absence of corridor patients is a genuine operational achievement rather than a statistical sleight of hand. The trust has also noted that its overall ambulance handover times remain better than the regional average, a point it says is being overlooked in the current criticism.

That defence does not fully address what the ambulance service is describing. Better-than-average handover times and extended waits in car parks are not mutually exclusive, and the question of whether patients waiting in vehicles outside constitute a form of care outside the hospital's accountability framework is one that NHS England has not yet publicly answered.

The episode reflects a wider tension in how NHS performance is measured. Regulatory targets are designed to change behaviour, and they do. The difficulty is that they change behaviour in ways that are not always anticipated. When the pressure falls heavily on one indicator, hospitals have an incentive to protect that figure even if the underlying problem migrates somewhere less visible. Corridor care targets reduced visible overcrowding inside emergency departments. Whether they have reduced overcrowding overall, or simply moved it to the car park, is a different question.

The governance committee has heard the evidence. What happens next, including whether NHS England reviews how handover delays are weighted against corridor care in its regulatory framework, remains to be seen.