Millions of people on benefits are overpaying their broadband bills, media watchdog Ofcom has said.
Only 3.5% of those eligible for cheaper broadband tariffs are benefiting from them, as firms are failing to promote the deals properly.
This means around four million UK households could be getting cheaper broadband, but only around 150,000 people are, Ofcom says.
Social tariffs are available as a low-cost broadband option for customers receiving benefits, and typically cost around £15 a month.
It means they'll pay less than half of the average household’s broadband for those not on benefits.
According to consumer group Which?, it could save the average customer £140 a year.
However, customers’ broadband speed can be slower when on social tariff plans.
Those switching may also incur an exit fee from their current supplier, but many firms waive this fee.
Social broadband tariffs are available to people getting Universal Credit, and some providers allow other benefit claimants to apply too.
This can include Pension Credit, Employment and Support Allowance, Jobseeker's Allowance and Income Support.
Although broadband providers do not have to offer customers social tariffs, they have been encouraged to by the Government and Ofcom.
A range of broadband providers offer social tariffs, including BT, Virgin, KCOM, Hyperoptic, G Network, NOW, Sky and Community Fibre.
Prices for the tariffs normally range from £10-£25 a month.
BBC ’s ‘Rip Off Britain: Live’ found that out of the four big providers who offer these tariffs, only one had information about it on its homepage.
In the programme, an 82-year-old woman managed to save £120 a year just by switching away from her original deal with TalkTalk.
A BT Consumer spokesperson said: "We're dedicated to keeping our customers connected and committed to supporting all our customers across the UK who are on low-incomes or facing financial hardship... and urge anyone who qualifies for our at-cost, social tariff to get in touch."
BT works with debt charities such as StepChange, which helps customers manage their bills and debt for free.
And working with the government's Breathing Space scheme, the provider also offers financially vulnerable customers three months of free broadband.
Broadband provider TalkTalk said in a statement that despite not offering social tariffs, it has partnered with the Department for Work and Pensions and offers job seekers six months of free internet.
