Patients are being discharged from Royal Preston Hospital late at night in a bid to free up beds.
Health campaigners and MPs say they are concerned about the practice, which it has been claimed can see people sent home from hospital as late as midnight.
But Lancashire Teaching Hospitals, which runs the site along with Chorley and South Ribble Hospital, insisted the latest patients would be discharged was up to around 9pm.
Vernon Allen, a pensioner from Freckleton who is a member of the patient watchdog Healthwatch Lancashire, was alerted to the issue after he said a friend was discharged from Royal Preston Hospital at 10pm.
Mr Allen, who is also a member of Lancashire Teaching Hospitals and North West Ambulance Service (NWAS) trusts, said: “I know for a fact this is happening. Patients are being discharged at 9pm, 10pm and 11pm.
“It’s not on. They are discharging patients up to midnight.
“I spoke to NWAS and they said they don’t like doing it - it’s the hospital that is short of beds. This is absolutely appalling. My friend was discharged at 10pm and they were waiting for an ambulance, so in the end his family came and got him.
“It concerns me greatly - just imagine an elderly person or a person who has not been well coming home to an empty or cold house if they live on their own.”
Ben Wallace, MP for Wyre and Preston North, said he had met with hospital chiefs to discuss the problem.
He said three factors were putting extra pressure on wards - bed-blocking, when social care support is not available in the community so vulnerable patients have to stay in hospital longer, people giving up on out-of-hours GP services and visiting hospital instead, and the reconfiguration of mental health services and closing of inpatient wards, which means more mental health patients visit hospital.
He said: “These three factors combined with a shortage of key staff in Lancashire in A&E meant last month for a day or two they cancelled elective surgery at the hospital to clear the backlog.
“They’re trying to keep that going so that’s why at the moment you see people getting late discharges, because if they stay in the beds it all backs up.
“The hospital have told me they’re confident that when they clear that backlog they will go back to being discharged at normal times.”
Chorley MP Lindsay Hoyle said he had also heard about the issue, and had raised it in a meeting with the trust’s chief executive, Karen Partington.
A spokesman for NWAS said it provided a dedicated patient transport service vehicle rather than ambulances to transport the patients, which operates up until 10pm from Monday to Friday in the Preston and Chorley areas.
After that time the hospital has to make its own arrangements such as ordering taxis.
She said: “This resource is controlled by the bed bureaux. As with any patient discharge undertaken by NWAS, we would ensure that the patient is treated with dignity, and safely taken into their home or place of residence.”
Lancashire Teaching Hospitals said patients were only sent home when it was safe to do so and the right support was in place.
Karen Partington said: “Patient safety is our first priority and we only ever discharge a patient from hospital when it is safe and appropriate to do so.
“The majority of in-patients are discharged during the day. However, some patients may be discharged in the evening, up to around 9pm, and also at the weekend.
“The discharge process for patients being discharged from an in-patient ward includes a checklist to make sure every patient has the appropriate support in place, including appropriate transport to take them home, ensuring family or friends will be at home to provide support if required, and that they have food available.
“Patients would not be discharged home if staff were in any doubt that their safety may be compromised - they would stay in hospital or until appropriate arrangements could made.
“Patients do not want to stay in hospital any longer than necessary, and we need to discharge patients when they do not need any further hospital care to make sure resources are available for those who need admission and treatment.”