Some patients on NHS waiting lists may already be in danger of breaking the 2008 18-week waiting time target, Department of Health director of access and choice Margaret Edwards told the NHS Confederation conference.
The NHS must offer a maximum 18-week wait between GP referral and treatment by December 2008.
Ms Edwards warned that, although the deadline was approximately 1,300 days away, some patients awaiting diagnostic tests were already in danger of breaching the target.
'Based on pilots we are doing with trusts, there are already patients waiting that long if you take into account all the diagnostic tests and different processes.
'We may already be putting patients on our waiting list that could potentially breach the target - That is a scary thought', she told delegates.
She also revealed the pilots showed that certain diagnostic tests were emerging as 'key areas' in meeting the target. She pointed to significant evidence that endoscopies were an area with 'large numbers and long waits'.
Ms Edwards announced that the DoH was 'drafting up a proposed set of rules' about how the waiting time would be calculated in readiness for issuing guidance in the autumn. The rules would determine 'what counts towards the 18-week target and what doesn't - how the therapies and diagnostics fit in'.
Ms Edwards said the rules would govern 'when the clock starts, when it stops, when a patient is suspended and when it restarts again.' . Trusts will not be removed from patient choice menus from 2008 if they fail to hit the 18-week treatment target, according to health secretary Patricia Hewitt.
Despite reports following comments from Ms Edwards at last week's NHS Confederation conference, Ms Hewitt reassured trusts that they would not 'lose NHS accreditation', even if they missed the December 2008 18-week waiting time target.
By then, patients will have free choice of any provider and Ms Hewitt reminded trusts that the NHS improvement plan safeguards patients' rights to wait for treatment at their preferred hospital, even if it will take longer than 18 weeks for an appointment.