Thousands of patients were waiting for routine treatment at Southern Health in July, new figures show.
The Prime Minister has said the NHS must "reform or die" as the Government publishes a major report on its future.
NHS England figures show 3,704 patients were waiting for non-urgent elective operations or treatment at Southern Health NHS Foundation Trust at the end of July – down from 3,927 in June, but an increase on 3,511 in July 2023.
None of those had been waiting for longer than a year.
The median waiting time from referral at an NHS Trust to treatment at Southern Health was six weeks at the end of July – the same as in June.
Nationally, 7.62 million people were waiting to start treatment at the end of July – unchanged from the end of June.
Prime Minister Keir Starmer has today said there will be no more money for the NHS without reform.
Addressing the King’s Fund annual conference in London, the Prime Minister said he would "accept the challenge" of fixing the NHS but warned it would be "measured in years, not months".
Sir Keir was responding to a damning report from surgeon and former health minister Lord Darzi, which lays bare the problems in the health service.
The rapid review, carried out in nine weeks, says the health service "is in critical condition, but its vital signs are strong".
It sets out widespread issues, including a failure to cut waits in A&E, missed targets for treatment and cancer care, alongside low productivity in hospitals despite investment in staffing.
Separate figures show 1.6 million patients in England were waiting for a key diagnostic test in July – the same as in June.
At Southern Health, 1,911 patients were waiting for one of nine standard tests, such as an MRI scan, non-obstetric ultrasound or gastroscopy at this time.
Of them, nine 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 67.7% of cancer patients urgently referred nationally began treatment within two months of their referral.
That was up slightly from 67.4% in June.
Tim Gardner, assistant director of policy at think tank the Health Foundation, said: "Lord Darzi’s diagnosis and the new figures published today lay bare the consequences of a decade of underinvestment in the NHS and the immense challenge for the new Government in reversing the NHS’ decline."
Mr Gardner added: "We need to shift more resources towards primary care and community-based services, NHS buildings and equipment must be modernised, and technology must be harnessed to improve care for patients. Only then will we make the NHS fit for the future."
Rory Deighton, director of the NHS Confederation’s acute network, warned "positive signs of progress could easily be lost" in winter.
"These figures reinforce just how much pressure the NHS is under and just how hard staff are working to improve performance and provide the best care possible for patients," he said.