The Care Quality Commission is to place a restriction on the number of patients that can be treated at an east London emergency department.

The regulator plans to cap the number of patients who can be admitted to the “majors” part of the Queen’s Hospital emergency department at times when people already admitted have been waiting too long to be transferred.

It aims to do this by placing a condition on the trust’s registration - the first time this has been done for an accident and emergency department.

The CQC is to meet with Barking, Havering and Redbridge University Hospitals Trust, which runs the hospital, the NHS Trust Development Authority, and commissioners to discuss how the imposed condition should be managed.

The trust has the worst A&E waiting times performance in London, according to latest figures.

The Department of Health target is for 95 per cent of A&E patients to be admitted, treated or discharged within four hours of arrival.

BHRT’s performance since 31 December 2012 stands at 78.2 per cent, 10 percentage points lower than any other London trust and 15 points below the London average.

Inspections in November and December found there were insufficient consultant and junior doctors in the A&E department.

Matthew Trainer, CQC deputy director in London, said: “Put simply, there are not always enough staff to care for the number of people who are attending the A&E and not enough beds being made available in the rest of the hospital.”

Trust chief executive Averil Dongworth apologised to patients.

“We fully accept the findings of the Care Quality Commission’s report,” she said in a statement.

She added: “The CQC highlights in its report that Queen’s A&E department was designed to deal with 90,000 attendances a year. We are now seeing around 132,000 people through the doors. It also confirms that Queen’s receives more blue light ambulances than any other hospital in London.”

A CQC spokeswoman acknowledged a cap on attendances at Queen’s might pose capacity problems for neighbouring hospitals but said the regulator was “not responsible for managing the implementation of its conditions.”

She added that there would be “an exemption for cases where to uphold the restriction would put someone at serious risk - so nobody should be turned away if they arrive in an ambulance in a crisis situation”.

NHS London chief executive Dame Ruth Carnall said the trust’s lack of progress was “not due to lack of effort on the part of frontline staff – nor is it due to the lack of money.

“Over £5.7m has been invested to support the trust over winter, and primary care trusts and local clinical commissioning groups have provided extra support.”