An investigation has been ordered into how a grandmother living in sheltered housing suffered injuries her family believes were the result of multiple rat bites.
Pamela Hudson, 75, was rushed to hospital from her council home in York with injuries to her face, body and arms.
Her daughter Jan Derry said a rat "gnawed" at her bedridden mother, inflicting 50 bite wounds at Glen Lodge, which is sheltered accommodation with extra care.
Health Secretary Jeremy Hunt said the Government had ordered an investigation into her case, after seeing pictures published in the Sun newspaper.
Mr Hunt said: " These pictures are appalling and show the suffering of a vulnerable woman who, along with her family, was stripped of her dignity and badly let down. Working across government, ministers are ordering an investigation which will be launched in the coming days.
"Whatever the sort of social care provider, patients have a right to expect the highest standards, and that is what we are determined to secure."
Mrs Derry told the Sun she thinks the rat probably got trapped in the bed and attacked her mother as it tried to get free.
She said: "When we got to the hospital they were wiping blood from mum's wounds. They put a bandage on, but the blood soaked right through within the hour.
"The thought of how many times she was bitten is awful.
"We fear it may have got trapped in the bed with her and just kept biting and biting. We don't know, and never will, if it was one or more."
Mrs Hudson died three months after the incident after she was transferred to different accommodation.
Earlier this week, City of York Council said it had investigated the incident but could not find the cause of Mrs Hudson's injuries.
Martin Farran, director of adult social care, said: "We have worked closely with, and provided support to, Mrs Hudson and her family throughout the investigation into this incident.
"It is with regret that, despite extensive efforts by professional experts, environmental health and independent inspectors, we have been unable to determine the exact circumstances of how Mrs Hudson's injuries occurred.
"Our thoughts are with Mrs Hudson's family, who are understandably distressed by what has happened."
Caroline Abrahams, director of Age UK, said the case was "the stuff of nightmares".
"Our care system is under so much pressure that no one can be 100% confident an older loved one will always be cared for as well as they should be," she told the Sun.