Pensions have been linked to inflation, which is around 2% a year, rather than average earnings, which are rising at about 4% a year, since 1980.

Baroness Castle: "The government promised in its manifesto that pensioners would share in rising prosperity"

About 2,000 pensioners - who get a basic £66.75 a week - cheered former Cabinet minister Baroness Castle of Blackburn as she laid out their case at a London rally.

"If Margaret Thatcher had not abolished the earnings link then the basic pension would not be £75 but £93 for a single pension," she said.

"That cannot be restored all at once - we are realistic and sensible in our demands - but we ought to go some way to restoring the gap. We are demanding that the basic pension is increased to £75 a week."

And she accused the UK Government of "dodging" the issue.

"Pensioners expected more from a Labour government but they have been deeply disappointed."

Listen up: Many pensioners have no other income to fall back on

The current basic pension - £8.25 less than the young and jobless receive on income support - is set to rise by 75p a week in April.

More than 11m people in the UK rely on the basic state pension, which is the lowest in Europe.

Pensioners are able to apply for income support to top up their pensions, but need to fill in lengthy application forms and many are reluctant to apply for what for they see as "handouts".

The BBC's Andrew Verity reports: "The organisers say the state pension must rise in line with average earnings"

Dr Gary Kitchen of the National Pensioners Convention, said: "People who have worked for 40 years and have paid their national insurance contributions are getting less than people on income support.

"The government will say that they can't afford it, but to increase the basic pensions to £75 would cost around £3bn and there is a surplus of £6bn in the National Insurance fund.

"We are marching today to bring our plight to the attention of the public. We need people to know what is going on.

"This isn't only about money it's about the state of society we live in and how old people are treated."

Other speakers at the rally included, Tony Benn, Labour MP for Chesterfield, trade union leader Jimmy Knapp, and prospective London Mayoral candidates, Ken Livingstone and Trevor Phillips and Observer newspaper editor Will Hutton.