Two mental patients escaped from Springfield Hospital three weeks after a report blasted security at the institution.

Despite the patients being caught in Edinburgh, the incident is a sign that little has changed at the Shaftesbury Clinic, the Tooting hospital's notorious medium secure unit which treats patients from Kingston.

Both men, who escaped on December 14, remain in police custody. A Metropolitan Police spokeswoman said: "We were notified at 12.50pm of two men having absconded from the secure unit at Springfield Hospital. They are serving prisoners who had been at the hospital for several months. Following inquiries, both men were arrested at 6.30pm the same day."

The hospital has refused to explain what happened, but Peter Houghton, chief executive of the South West London and St George's Mental Health NHS Trust, said: "A full investigation is under way. A member of staff has been suspended and we have temporarily closed the unit to new admissions.

"This highly regrettable incident strengthens our determination to implement the action plan drawn up as a result of the John Barrett inquiry."

Criticism is mounting coming so soon after the Barrett report. The inquiry had investigated the death of retired banker Denis Finnegan who had been fatally stabbed by John Barrett in Richmond Park on September 2, 2004, after he escaped from Shaftesbury Clinic.

The report concluded the death resulted from "systemic failures" by the trust and stated: "We question whether the Shaftesbury Clinic should continue to operate as a medium secure unit."

Councillor Ian Hart, chairman of the health committee, said: "Residents are losing confidence in the hospital's ability to keep secure units secure. There's no evidence of change. It's time for action and a guarantee that security will to be sorted."