Prime Minister Cameron is believed to have some sympathy for expat pensioners whose state pensions have been frozen, according to one MP fighting to change the policy.
At present, pensioner expats in certain countries, often commonwealth ones, have their pensions frozen at the time of retirement without benefitting from inflation-linked rises.
Sir Roger Gale, the Conservative MP for Thanet North, said he had recently met David Cameron to lobby him for change. He said the Prime Minister was "not unsympathetic" over their plight but that no change was imminent.
But he added that while the Prime Minister himself had been sympathetic, others in his office had not. "The attitude towards expat pensioners was 'they don't vote, do they'."
A new cross-party parliamentary group formed to campaign against the practice met for the first time on Monday.
The initiative is supported by the governments of Australia and Canada which often wind up providing financial support to British pensioners who have been short-changed.
David MacClennan from the Australian High Commission said Britain's failure to pay full pensions to expats in Australia was the "biggest bilateral issue" between the two countries.
"We always raise it at meetings," he said. "We wholeheartedly support this campaign."
Chris Chant from the Canadian High Commission said: "Our sentiments are similar, this is a question of simple fairness. This issue comes up between us and the UK all the time."
