Benefits may not be claimed when people are unaware of their rights
Targets need to be set to ensure more people claim the benefits to which they are entitled, a coalition of charities has said.
About £16bn in income-related benefits and tax credits goes unclaimed in the UK in a year.
Now 27 charities, led by Citizens Advice, has called on the government to set "ambitious targets" for the take-up of these benefits.
The government said action was being taken to help people claim.
The charities are drawing on figures published by the Department for Work and Pensions in June, which showed that up to £10.5bn in income-related benefits went unclaimed in 2007-8.
A calculation of take-up of the five key benefits - Income Support, Pension Credit, Jobseeker's Allowance, and housing and council tax benefits - showed that the estimated amount that went unclaimed shifted up slightly, as compared with a year earlier.
The other set of data came from HM Revenue and Customs, showing that about £6.2bn of child tax credits and working tax credits were unpaid in 2006-7.
The charities said:
- Four in five low-paid workers without children missed out on tax credits worth at least £38 a week
- Up to half of all working households do not claim housing benefit worth an average of £37.60 a week
- An average of £13 a week in council tax benefit is not being claimed by up to three million households
- Up to 1.7 million pensioners are missing out on an average of £31 in pension credit payments.
"This adds up to millions of people in dire need missing out on the help they should be getting to make ends meet," said Citizens Advice chief executive David Harker.
"This is bad news at any time, but it is especially worrying when so many are still feeling the impact of the recent recession."
He said that claims were not made owing to the complexity of the system, as well as some people being unaware that they were entitled to the money.
He said he wanted a similar focus on cutting unclaimed benefits as on catching benefits fraudsters.
This is not the first time that the issue has been raised, and various reports have been commissioned by the government.
The benefits system has also changed in recent times, with pensioners given the opportunity to ensure they have a series of connected benefits rather than applying for each in turn.
"We want to make sure that everyone is getting the help that they are entitled to," said a spokeswoman for the Department for Work and Pensions.
"We have made it more simple and straightforward to claim Pension Credit, Housing Benefit and Council Tax Benefit together in just one free phone call. We make 13,000 home visits every week to ensure that vulnerable pensioners are getting the help they need.
"HM Revenue and Customs have set up an online calculator so that people can find out quickly and easily if they are eligible for working tax credits with the goal of getting 100,000 more people claiming this important support by next year."