A hospital trust has revealed it failed to properly record the waiting times of 60 per cent of its elective inpatients, causing hundreds of them not to receive treatment within the 18-week deadline.

North West London Hospitals Trust admitted it failed to start the clock when 2,700 people on its inpatient waiting list were referred to it for treatment. The news was overshadowed by emerging this week - the same week in which health secretary Jeremy Hunt gave approval to proposals to downgrade emergency department facilities at four hospitals in its area.

The national target is for 90 per cent of patients to be treated within 18 weeks of referral from a GP.

The trust said approximately 800 patients who had not previously been recorded in the system had breached the 18-week target and 12 patients had waited more than a year.

Chief executive David McVittie said he became aware of the problem late last year and the Department of Health’s intensive support team on elective waits was called in February, following an internal investigation.

Mr McVittie, who joined the trust in July 2012, said a further investigatory panel was being set up, including both trust staff and external figures, but the indication so far was that no patients had been harmed.

In addition, a report to the £380m-turnover organisation’s board said: “There was a culture where some staff felt under pressure to stop patients’ clocks prematurely and therefore accurate times were not recorded.”

It also said there were no standardised waiting-time recording procedures for junior clerical staff across different divisions.

The trust also said there could be a fundamental problem with its capacity to deal with the volume of referrals it received.

The report said: “Over time demand for particular services had built up but without the necessary capacity in place, and the amount of care commissioned was insufficient.”

The trust said the “vast majority” of the patients affected had now been offered an appointment and the remainder would be offered dates within the next four weeks.

Mr McVittie said the trust was trying to perform as much of the backlog work as possible at its two sites, Northwick Park Hospital and Central Middlesex Hospital, but that some of it might have to be dealt with by other providers.

He added that some of the work could also go to Ealing Hospital, with which North West London Hospitals Trust is trying to merge, and of which he is also chief executive.

It is not known how much the extra work will cost commissioners.

The organisation is also reviewing its data processes for all other waiting time measures except that for accident and emergency.

Mr McVittie said the investigatory panel, which has its first meeting next week, would be making any decisions about disciplinary action against staff.

The trust has had two interim chief executives since January 2011.

Mr McVittie said if the same thing had happened when he was chief executive at Hillingdon Hospital, where he was in the top job for 11 years, then he would have taken responsibility for the culture that had developed at the trust, but he had inherited a difficult situation at North West London Hospitals.

The trust is is predicting a year-end deficit and has significant performance issues in A&E. The most recent weekly data indicated 88.3 per cent of type-one patients seen within four hours, against a national target of 95 per cent.

The trust appointed a new interim director of operations, Tina Benson, in February this year, and chief operating officer, Chris Pocklington, in April.