A third of families rely on grandparents to provide childcare, according to a damning report on the effect of high childcare costs on older relatives.

The report by Grandparents Plus and the Equality and Human Rights Commission found that single-parent families and those on low incomes are among the most reliant on grandparents due to the "prohibitively expensive" cost of childcare.

The report, called Protect, Support, Provide, estimates that half of all single-parent families rely on grandparents for childcare.

Providing childcare is having a devastating effect on grandparents' finances, adds the report.

Around a third of all family and friends who care for a child say they have to give up work or reduce their working hours.

Three out of four family or friend carers say they experience financial hardship when taking on the care of a child.

Ethnic minority families and families with a disabled child are also among those most likely to use grandparents for childcare.

The report warns the government that this trend in grandparental care means its policy of encouraging lone parents into work is at odds with its aim of increasing the employment rate among those approaching pension age.

It also calls for the government to give grandparents who provide childcare more financial, emotional and practical support.

Sam Smethers, chief executive of Grandparents Plus, said: " It's time the government recognised that grandparents provide the last line of defence between millions of children and the poverty line. They need recognition and better support."