A large hospital trust has been caught altering waiting time figures to avoid breaches of the four-hour accident and emergency target.

Barnet and Chase Farm Hospitals Trust in north London was investigated after a complaint in summer 2012 that patients were being sent to wards before they were ready or properly staffed; placed in an “observation unit” to avoid breaching the limit; and that the time taken to assess patients was being misreported.

The Department of Health target says 95 per cent of patients in A&E must be seen, treated, admitted or discharged within four hours from arrival.

An investigation, commissioned by the trust after its chief executive was alerted to the issue, found evidence of the trust “misreporting” waiting times. It said “developing inappropriate methods to avoid breaches had become accepted practice within A&E at Chase Farm”.

It found no evidence of harm to patients but one its findings said: “The allegation that patients are sometimes taken to the wards before ward staff are ready and on occassion without receiving essential first-line medication is correct.”

Investigators found no proof that staff had been “pressurised to misreport data by managers” but added “we believe [pressure] came from a collective ‘sign up’ by senior managers to minimise breaches”.

The review was carried out by healthcare investigation firm Verita and will be discussed by the trust’s board on Friday.

It said no one individual was to blame but that a culture of misreporting had developed at Chase Farm.

In November chief executive Mark Easton stepped down, and he has since been seconded to NHS London.

At the time Barnet and Chase Farm said it was “an appropriate time” for him to step down as proposals for capital works at the trust had been submitted and the case for merging with the Royal Free London Foundation Trust submitted.

The report said the chief executive should determine if anyone ought to face disciplinary action and the trust would not confirm if any staff had been disciplined.

Barnet and Chase Farm did confirm that director of operations for emergency care Sarah Perry no longer worked at the trust.

A spokesman for NHS London said: “It is not acceptable to falsify any performance figures and we take this matter very seriously. 

“[Mark Easton] contacted Verita when this was raised by the whistleblower and took urgent action in response to the Verita report. This independent report has found that the misreporting of figures was accepted behaviour and became part of the culture in the departments involved. We have been assured by the trust that this has been rectified and we are monitoring them very closely. 

“It is vital that all patients are seen quickly in A&E and receive the highest standards of care. As we begin to handover to clinical commissioning groups, we have written to all PCT clusters in London to firmly hold their trusts to account and ensure rigorous checks are in place to make sure this does not happen again.”

NHS London is being abolished in April and a similar role will be carried out by a regional team of the NHS Commissioning Board.

A previous major instance of a trust admitting the misreporting of A&E figures was at West Middlesex University Hospital Trust in 2009.

That case saw the resignation of its chief executive amid allegations of the falsification of data on the trust’s IT system in A&E.

In a statement trust chair Baroness Margaret Wall and interim chief executive Tim Peachey said: “On behalf of the trust board, we would like to apologise for this unacceptable incident, and we can assure you that the board has accepted all the recommendations from the report.  

“Whilst patients did not come to any harm, we have taken immediate and robust actions to ensure our patients are treated appropriately, in a timely manner and that the A&E waiting times targets are accurately recorded and reported.”