Northampton General Hospital A&E saw its "busiest day ever" this week with over 400 patients asking for help in a single day.
The hospital has been running at the highest level of escalation - OPEL 4, previously known as "black alert" - for most of the week, meaning the lack of free beds might send patients out of town for treatment.
The department also saw its second busiest day ever this week, but hospital officials say they were able to deal with the record numbers and managed to see four-out-of-five patients within four hours.
Northampton General Hospital A&E saw 402 patients on Monday and 355 on Tuesday.
A spokeswoman said: “This week we’ve seen unprecedented numbers of patients attending our A&E department. When faced with such intense and sustained pressure we prioritise the safety of our patients above everything, including targets.
“Our recent CQC inspections praised our culture of putting patient safety above all else. We are sorry when patients sometimes have to wait longer than we, or they, would like to be treated or admitted to a hospital bed, but they will be cared for safely while they wait."
In February, the hospital spent 12 days on "red alert" and 14 days in total on "black alert". This meant hospital staff had to have 'crisis' meetings every few hours to assess their capacity and care priorities, while 38 operations were cancelled.
A new £12million assessment centre to take the strain off A&E is under construction at the hospital - but is not scheduled to open for another year, in mid-2018.
The hospital is urging patients to get early help from their pharmacist or GP when they start to feel unwell.
A spokeswoman said: “Our local community can help us in a number of ways. We urge people to get help early from their pharmacist or GP when they start to feel unwell, especially if they’re managing a long-term condition because getting help early could prevent a hospital admission later.
"We’d also urge people to keeping on top of ordering their repeat prescriptions and have a flu jab if they’re eligible.
"People with relatives in hospital can also assist by being ready to help their loved ones return home or to their place of care when they are ready to be discharged."
No exact cause is known for the heavy caseload at A&E on Monday.