The basic state pension is set to go up by just over £3 a week to £87.30 from Monday.
Increases announced by the Government in December's pre-Budget report will also see the pension credit guarantee rise by £5 a week for a single person and £7.65 for a married couple.
It means that the UK's poorest pensioners will now see a minimum income of £119.05, rising to £181.70 for a couple.
The basic state pension goes up in line with inflation but is due to be re-linked with earnings in the next Parliament, possibly as early as 2012.
Commenting on the annual increase, Age Concern called for greater work to ensure that pensioners receive all that they are entitled to.
Gordon Lishman, director general of Age Concern, said: "With state benefit going up, it is more important than ever for older people to find out if they might be entitled to some extra cash and put in a claim.
"Rocketing household bills over the past few years have put a major strain on the finances of many pensioners, yet up to £4.2 billion in money benefits is left unclaimed by older people every year."
He added: "It is really worrying that some of the poorest and most excluded older people are missing out on money that is rightfully theirs because they don't know that they are entitled, are worried about the complexity of the process or are embarrassed about claiming."
