Thousands of military partners may be missing out on pension payments worth thousands of pounds, it has been claimed.
Last year the government launched a system of National Insurance credits to help the spouses of those who spent time overseas because of their partners' military service.
When it was launched the Ministry of Defence said it would benefit up to 20,000 people but information requested under the Freedom of Information Act by Royal London showed fewer than 4,000 people have applied for it.
Those who do not claim this credit could miss out on up to £30,000 in state pension over the course of their retirement.
Sir Steve Webb, former pensions minister and director of policy at Royal London, said: "Women should not be suffering in retirement for their loyal service alongside their husbands overseas.
"The government should not simply wait for people to claim but should actively identify those who might be eligible and make sure that they get the money that they are entitled to."
In order to access the extra pension payments, spouses must apply for a credit for any week when they were outside the UK alongside their partner.
But the Department for Work & Pensions has disputed the figures and said the number of applicants did not reflect the scheme's success.
A spokesman for the DWP said: "These figures are misleading and based on flawed assumptions. Our 20,000 estimate covers the period up to 2066 so applicants in the first 18 months isn’t indicative of a low take up at all
"Our armed forces protect our country and it is only right that in turn, we help protect their partners' ability to receive the full state pension when they reach state pension age and we would encourage everyone to check their eligibility online."
The credit can be claimed back to 1975 and a full financial year of credits counts as one year towards the 35 needed for a full state pension.
It can also be claimed by widows and those who are divorced.