Actress Phyllida Law has spoken out about the frustrations of caring for a parent with Alzheimer’s disease.

Ms Law, the mother of Oscar-winner Emma Thompson, looked after her own mother Meg, who lived with the family for 17 years as the degenerative illness progressed.

She said: "The night time was particularly difficult: at dusk my mother would often think she was in the wrong house, or she would call for breakfast in the middle of the night, not knowing what time it was. When you're worn out because you haven't slept, you can be in danger of losing your temper, and that's very hard.

"I wasn't as isolated as some people, and I was lucky because I had help from the people in my mother's village and from my two daughters, who also helped me financially. But caring for ma, you couldn't leave the house without taking her with you, so you did feel very stuck a lot of the time."

The Olivier Award-winning actress is most famous for her work in Four Weddings and a Funeral and Harry Potter and the Deathly Hallows.

Ms Law was also married to the Magic Roundabout author Eric Thompson, who died from a heart attack in 1982.

She has previously stated that the character of Ermintrude the cow was modelled on her.

The Glasgow-born actress wrote about the difficulties of caring for her mother in her book ‘Three Mothers (and a camel)’ which was released in 2014.

In the book, she recounts how she caught ‘Mego’ talking to herself in the mirror and prepared medicinal G&Ts for her mother.

Mego died in 1994 aged 93 after almost 20 years of being cared for by Ms Law at her mother's home in the village of Ardentinny on the west coast, near Dunoon.

Now 83, Ms Law lives in West Hampstead, London, on the same street as her daughter, actress Emma Thompson.

Law has been a long-time supporter of charity Alzheimer’s Research UK and her frustrations and worries from her time as a carer reflects new findings from the charity.

The report, Dementia in the Family: impact on carers shows that 31 per cent of people over the age of 55 are worried that they will have to rely on their families for care in later life.

Through polls and interviews with families affected, the report looks at the how looking after someone with Alzheimer’s seriously affects the life of a carer.

Hilary Evans, chief executive of Alzheimer's Research UK, said: "For many people the festive season is a time to think about family, but for countless families across the UK dementia is taking a heavy toll, leaving people socially isolated and struggling financially.

"The experiences highlighted in this report will be recognised by people up and down the country who are dealing with the challenges of caring for a loved one with dementia."

Alzheimer’s Research UK spokeswoman Kirsty Marais said: “We really were interested to see what the results of the poll were. We didn’t know what to expect or what people were worried about.

“The main aim is to highlight the stresses but people do say that they are rewarded by the work. Dementia changed family relationships, often children find that they have to look after their parents in a way that they were looked after when they were younger. We really need to underline the need to help people who have care for family members.”