Thousands of patients were waiting for routine treatment at Southern Health in November, new figures show.
It comes as Health and Social Care Secretary Wes Streeting warned "it will take time to turn the NHS around".
NHS England figures show 3,679 patients were waiting for non-urgent elective operations or treatment at Southern Health NHS Foundation Trust at the end of November – down from 3,838 in October.
None of those had been waiting for longer than a year.
The median waiting time from referral to treatment at Southern Health was six weeks at the end of November – up from five weeks in October.
Nationally, 6.28 million people were waiting to start treatment at the end of November — down from 6.34 million at the end of October, and the lowest figure since May 2023.
Tim Gardner, assistant director of policy at the Health Foundation, welcomed the drop but warned improvements must still be made.
He said: "NHS trusts declaring critical incidents this week serve as a stark reminder of how difficult winter has become for our health service.
"Improvements need to be made across the system, including investment in additional capacity in both primary and acute care, new technology and skills to streamline services and boost productivity, as well as long overdue reform and investment in social care."
Separate figures show 1.6 million patients in England were waiting for a key diagnostic test in November – the same as in October.
At Southern Health, 2,884 patients were waiting for one of nine standard tests, such as an MRI scan, non-obstetric ultrasound or gastroscopy at this time.
Of them, 80 (3%) had been waiting for at least six weeks.
Other figures show cancer patients across England are not being seen quickly enough.
The NHS states 85% of cancer patients with an urgent referral should start treatment within 62 days.
But NHS England data shows just 69.4% of cancer patients urgently referred nationally began treatment within two months of their referral.
That was up from 68.2% in October.
Professor Pat Price, chair of Radiotherapy UK, said: "Today’s updated NHS cancer waiting list data underscores the urgency of delivering a national cancer plan and why it must be big, brave, and bold.
"While the Government has promised that this is the year we will finally see the national cancer plan, every day that goes by sees more patients fall through the cracks."
Professor Price added a long-term strategy for cancer "cannot come soon enough" and must ensure cancer patients have access to curative radiotherapy.
Health and Social Care Secretary Wes Streeting warned "it will take time to turn the NHS around" despite an encouraging fall in treatment waiting lists across the country.
He said: "Despite the best efforts of staff, patients are still receiving unacceptable standards of care.
"It will take time to turn the NHS around, but the fact that waiting lists are now falling shows that change is possible.”
He added the new elective reform plan, launched on Monday, will support better elective care services and an improved experience for patients.