Official statistics reveal 1,436 people were delayed in being discharged from hospital when a census was taken in June, up 10 per cent from 1,300 in June 2017.
Delayed discharge - also known as bed blocking - occurs when patients are fit to leave hospital but are unable to, often due to a lack of social care.
Age Scotland said older people put off going into hospital for fear of becoming “stuck” in the system and called on ministers to act.
Health Secretary Jeane Freeman said nearly £500 million is going to health and social care to drive down delayed discharge.
Of those patients affected in the June census, the vast majority - 1,187 - were delayed for more than three days.
For almost three-quarters (74 per cent) this was due to health and social care issues, followed by having complex needs for 23 per cent and patients and family reasons in 3 per cent of cases.
A total of 573 patients at the census point were delayed for more than four weeks while 28 had been waiting to leave for more than a year.
The daily average number of beds blocked rose for the sixth consecutive month to 1,413.
In total, patients spent 42,375 days in hospital due to delayed discharge in June, up 8 per cent from 39,252 in June 2017.
Age Scotland claimed this increase would cost around £727,000, based on an average of £233 a day.
Chief executive Brian Sloan said: “Around four in 10 people who are ready to leave hospital are waiting more than a month to do so. This is scandalous.
“Keeping people in hospital longer than necessary delays the start of their recovery, puts them at risk of infections, causes loss of mobility and can have a devastating effect on their mental health.
“It also exacerbates feelings of loneliness and social isolation which becomes harder to overcome once they’ve been discharged.
“We know of older people who see these figures and avoid visits to hospital at all costs for fear of being stuck in the system, unable to leave.
“These figures are steadily worsening and must serve as a wake-up call to the Scottish Government, if the bells aren’t already ringing.”
Ms Freeman said: “June has seen a 2 per cent decrease in bed days lost to delay compared with the previous month.
“During 2017/18, we achieved a 7 per cent reduction in bed days lost to delay and we are looking to continue that overall progress this year.
“To support that, we have transferred nearly half a billion pounds from the NHS into social care and integration this financial year, and the health budget will increase by almost £2 billion 2021.”