More than one in 10 providing unpaid care
The number of unpaid carers in England and Wales has reached 5.8 million - a rise of 600,000 since 2001, the Office for National Statistics (ONS) has said.
Figures from 2011 show that the largest increase was in unpaid carers working for 50 or more hours a week.
Wales had a higher percentage of people providing unpaid care compared with any English region.
In England, the highest percentages of unpaid carers were in the North West, North East and West Midlands.
The ONS study into unpaid care in England and Wales, 2011 found that more than 12% of the population in Wales provided some level of care in 2011.
The rise in those providing over 50 hours a week of unpaid care means that across England and Wales there are now 1.4 million people providing round-the-clock care - an increase of 270,000 people since 2001 (25%).
Across local authorities in England and Wales, the number of carers increased in 320 authorities and fell in just six.
In Birmingham, the number of unpaid carers increased by more than 9,000 between 2001 and 2011.
Across English regions and Wales, the provision of between one and 19 hours was the most common level of care provided.
London was the area with the lowest percentage of unpaid carers at 8.4%.
The study said London's lower level of care provision was likely to be influenced by its younger age structure, the transient nature of its population and differences in household composition.
The provision of unpaid care is an important statistic, the ONS says, because unpaid carers make a vital contribution to the supply of care but their role can also affect their employment opportunities as well as their social and leisure activities.
Unpaid care means care provided to family members, friends, neighbours or others who are disabled, elderly or have long-term health problems. It does not include people providing general childcare.
Heléna Herklots, chief executive of Carers UK said: "Family life is changing as a result of our ageing population and the fact that people are living longer with disability and long-term ill-health.
"Too often the costs and pressures of caring for older or disabled loved ones can force families to give up work to care and lead to debt, poor health and isolation.
"In addition, as more families need help to care, social care support and disability benefits are being cut. This risks putting even more pressure on families, many of whom are already struggling to cope."