Hundreds of thousands of Britons retired overseas stand to win £3.9bn in increased pension rights from the Government when they take their claim to the High Court in April.
The test case could benefit half a million British pensioners living all over the world who have had their pensions frozen to rates set in the 1950s. Many live on or below the poverty line.
Lawyers, including barristers from Cherie Booth's chambers, are to use the Human Rights Act to argue that pensioners living outside Britain are being discriminated against by not receiving full state pensions. The case which comes after a twenty year battle is being brought by 33,000 pensioners living in South Africa.
Manchester-born Marjorie Ferreira, 68, who has lived in Durban for 33 years could barely afford the £3 it takes to join the campaign the South African Alliance of British Pensioners is waging against what they call "pension apartheid".
"We are standing up for our right, which is an end to discrimination against Britons living abroad," the feisty grandmother said.
"Why should I get £14 when in the UK I would get £72.50 a week, a house, telephone and Meals on Wheels?" .
The "pittance" Mrs Ferreira gets from the British government barely covers food and a small insurance. If it were not for the modest income of her South African husband, the former Wren and hat factory worker would be destitute.
The British policy Mrs Ferreira wants scrapped was adopted soon after the Second World War. It freezes pension levels for most of those living abroad at the rate fixed when they left Britain. While some countries, such as Jamaica and the US, have secured pension increases for ex-pats in bilateral agreements with Britain, most have not and ex-pats there continue losing out.
Over the years, they have been powerless to do anything but watch bitterly as the older they get, the poorer they get, their fixed income, in some cases just a few pounds a week, eroded by inflation.
The Alliance's general secretary Eric Byrom, 69 said: "People feel disenchanted about being encouraged by the government to live abroad , and then being abandoned".
London solicitor Graham Chrystie of law firm, Vizards Wyeth is representing the South African pensioners. "Every year, all pensioners at home and 440,000 abroad get an increase, and 550,000 do not," said Mr Chrystie.
"I believe Britain's treatment of ex-pat pensioners has been one of the most disgraceful episodes of post-War governments. Colleagues in Europe can't understand how they have got away with it. If we win, we're hoping to open the door to unfreezing of all UK pensions in countries where people have been deprived."
Mr Byrom, who retired in 1991, is stuck on £52 a week, and he knows a couple in Johannesburg whose joint pension was frozen at £13 a week: "She is 91, ill and having to choose between food and medication." Their British pension puts them below a South African poverty line covering little more than enough food to survive.
Many pensioners, Mr Byrom said, are "suffering terribly, especially old people stuck on very low pensions, who have no other savings and nobody to help support them."
The High Court in London will now rule on the challenge at a judicial review hearing on 15 and 16 April.