More than 700 patients waited too long for ultrasound tests at Kingston Hospital because of staff shortages, GPs have been told.
Health services across the borough must ensure 99 percent of patients needing a diagnostic test are seen within six weeks.
Kingston’s clinical commissioning group reported this month the figure stood at just 82.8 percent in December.
A governance report said: “The issue is at Kingston Hospital and all in non-obstetric ultrasound.
“The problem was originally caused by the resignation of the lead sonographer and an inability to recruit a replacement.
“There has also been sickness of another sonographer leading to a backlog developing.”
The backlog of 728 patients has been cut to 468 after extra services were put on at Surbiton Health Centre and elsewhere.
The 99 percent target is expected to be met by the end of March.
A Kingston Hospital spokeswoman said: “Since May last year, there has been an unprecedented demand for ultrasound services and this led to a temporary increase in waiting times.
“The demand has been caused by a large increase in referrals and as a result we have been working with Kingston CCG and other radiology colleagues to increase capacity and ensure that we can provide a better service for our patients and community.
“We are now on track to have cleared the backlog by the end of March and waiting times will be back to normal.”