About half the care homes in the South East have been told to improve, with inspectors finding homes "smelling of urine".
Figures released to the BBC over an 18-month period show 44% of homes in Kent, Sussex and Surrey were rated inadequate or requiring improvement.
The Care Quality Commission (CQC) said the number of homes told to improve was "too many".
One inspection said a person had gone a month without a bath or a strip wash.
Another found residents often had no toilet paper and another described a strong odour of urine.
One inspection took place when it was 35C outside and the heating inside the home was switched on.
Fewer than 1% of homes were classed as outstanding.
The quality of care homes in the South East was recently placed under the spotlight over deaths at the scandal-hit Orchid View home, in West Sussex.
In October 2013 a coroner ruled 19 residents died after "sub-optimal care", with five of them suffering "neglect".
Orchid View in Copthorne, which was run by Southern Cross, closed in 2011.
Lesley Lincoln, whose mother died at the home, said she was "not surprised" by the latest figures.
She said: "To say they [the CQC] are walking into homes with the smell of urine so strong it caused tears in their eyes - you think, why is that only being discovered now?"
Ernie Graham, who owns the Graham Care Group, which has a number of homes in the South East, said prior inspections focused more on whether standards had been complied with.
He said: "Now there's a lot more how the resident feels on the day - there needs to be a wider picture taken into account as well."
Nadra Ahmed, who is the chairwoman of the National Care Homes Association, claimed low government investment in adult social care was a contributing factor.
"Providing the care is becoming more and more difficult," she said.
"Sometimes it is the environment letting people down and primarily it looks like paperwork is a major issue."
Gail Stirling, head of inspection for the South East CQC, said there was a "mixed picture" across the region into terms of care standards.
She said: "The 45% is too many and we want to see that improve.
"I'm always disappointed to hear when people aren't receiving good care. Everybody has a right to expect good care."