A "growing army" of nearly 4,500 people spend more than 50 hours a week providing free care for family or loved ones.
The figures released by the Office for National Statistics showed the number of people in the Westcountry tending to family or friends dramatically rose over a ten year period to almost 200,000.
Unpaid carers in Devon and Cornwall who are mainly women looking after elderly people grew by almost 25,000 from 2001 to 2011.
Every area across the two counties saw a jump in the proportion of people spending upwards of 50 hours a week on unpaid care.
Torbay had the biggest proportion of its carers in that category with 580 (3.6%) out of a total of more than 16,000 carers.
James Drummond, carers lead for Torbay and Southern Devon Health and Care NHS Trust, said unpaid carers paid an "extremely valued role" in communities. But he warned of an unknown number of hidden carers who weren't able to get support.
Mr Drummond said: "Torbay is one of the leading areas nationally, in terms of the proportion of carers getting support, but we still have a long way to go. We know that many carers remain hidden and this is partly due to the fact that many of them take on the role very gradually and don't see themselves as a carer."
The South West, including Gloucestershire, had the largest increase of all regions with an additional 109,602 unpaid carers since 2001.
The latest figures have been blamed on the ageing structure of the South West population influencing the underlying need for care, and led to calls from care groups and unions for greater help and recognition of carers.
Heléna Herklots, 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.
"Far too many women are forced to trade down or even quit jobs when they take on caring responsibilities."
In Plymouth carer numbers grew by more than 3,000 over the decade. A spokesman for Plymouth City Council said it would do "everything possible" to support those who look after friends and family members.
Research suggests that people providing unpaid care are at increased risk of psychological stress, depending on their age and job.
The general trade union GMB, whose members include workers in health care and the ambulance service, said more care should be provided through the public sector.
Frances O'Grady, general secretary of the TUC, said: "Britain's growing army of unpaid carers, the vast majority of whom are women, provide an invaluable service to society. But despite being worth around £340bn a year, unpaid care is still not given the recognition it deserves from either the Government or employers."
In England and Wales there were approximately 5.8 million people providing unpaid care in 2011, representing around one tenth of the population.