One of England’s largest hospital trusts has taken the rare step of suspending its reporting of three key performance measures as it is “unable” to determine how many patients are waiting for treatment.

Imperial College Healthcare Trust in London will not report its elective care referral-to-treatment times or cancer or diagnostics wait statistics to the government for six months, breaching Department of Health reporting standards.

The £920m turnover trust said “significant anomalies” in the data meant it would not be reporting these outcomes from January to June this year and that an external review had been ordered.

The decision was taken after a review by the DH’s intensive support team found the trust was “unable to provide sufficient assurance over the size of the admitted and outpatient waiting lists”.

In his report to the trust board last week, interim chief executive Mark Davies said: “The board needs to understand that the position the trust is in is serious and the cessation of reporting is a significant step. However, the executive team believes it is essential to take this step in order to allow the time required to address the complex and significant system issues.”

The trust is now asking its commissioners, principally the north west London primary care trust cluster, for financial support to tackle the 18-week backlog, thought to total more than 2,000 patients. This could mean treatment in other NHS trusts or the private sector.

The board said it would work towards “clearance of the admitted waiting list over 18 weeks” to get it “down to no more than 1,000 by 31 March”.

The backlog could have caused NHS London to miss its referral-to-treatment target for elective care, whereby 90 per cent of patients must be treated within 18 weeks. It scraped by with 90.5 per cent.

A DH spokesman said: “We would expect the suspension to be as short as possible in order to correct their procedures and for formal reporting to resume as soon as possible.”