Thousands of carers could be missing out on valuable rights which would help them build a bigger state pension, figures obtained by a mutual insurer suggest.
Royal London said a scheme designed to help carers of disabled people build better state pension entitlement has failed to reach many of its target group, according to a response it received to a freedom of information (FOI) request.
The FOI reply received from the Department for Work and Pensions (DWP) indicates that 3,524 people claimed the national insurance credit in 2016/17.
An earlier estimate when the scheme was introduced said that 160,000 carers could benefit.
But the DWP pointed out that the figures Royal London refers to only cover successful claims made in 2016/17.
It said as of October 2017, more than 13,700 people were receiving carer's credit.
Royal London and Carers UK argued there should be a more proactive approach from Government to make sure that carers take up these rights.
Royal London estimates that each year of credits would add £237 per year to a carer's state pension, or over £4,700 over the course of a typical 20-year retirement.
A DWP spokesman said: "Over the past eight years the number of applications for carer's credit has consistently increased year-on-year.
"It is vital that carers get the support they need, which is why we work closely with disability and carer charities and groups, the media and provide information on gov.uk to raise awareness of this important benefit."
In 2010 a new system of national insurance (NI) credits was introduced to help bridge gaps in people's NI records, which are used to determine how much state pension someone is entitled to.
It was aimed at those who were spending at least 20 hours caring, affecting their ability to earn enough to pay NI, but who were not entitled to the carer's allowance for people doing 35 hours per week of caring, which has automatic credits for NI.
To qualify for the credit, a person aged under state pension age must be providing 20 hours per week or more of care for a disabled person who is receiving various allowances or payments.
If the person being cared for does not receive one of these benefits, the application needs to be signed by a health or social care professional such as a GP who can confirm the details on the application.
Sir Steve Webb, a former pensions minister who is now director of policy at Royal London, said: "It is time for proactive communications with those who are meant to benefit so that far more people get the help to which they are entitled."
Emily Holzhausen, director of policy and public affairs at Carers UK, said: "Caring often impacts negatively on health, wellbeing and ability to work and yet carers' contribution to the economy is worth billions a year. They should not lose out financially in retirement as well."
Information on how to claim the carer's credit can be found at: www.gov.uk/carers-credit.