The Women Against State Pension Inequality (WASPI) campaign has gained the backing of trade union Unison, which pledged to offer national support and funding.
Unison said it will provide WASPI with a "generous and considerable" financial donation that will be used towards the campaign's running costs.
The WASPI campaign began in 2015 and challenges changes to the state pension age (SPA) for women, first made in the 1995 Pensions Act and later accelerated in 2011 - it argues the reforms placed an unfair burden on hundreds of thousands of women born in the 1950s.
Under the 1995 Pensions Act, the government indicated the official SPAs of both men and women would be equalised by 2020. Previously, women retired at 60, while men stopped work at 65.
In the 2011 Pensions Act, SPAs were raised at an even faster rate. As a result, some of those born between April 1951 and 1960 will not qualify for a pension until the age of 66.
WASPI says some women had little notice, or were unaware entirely, that they would not get a pension at 60.
According to the WASPI campaign website, a deal with Unison had been struck just before Christmas.
The campaign is also expected to feature heavily on the agenda of the Unison Women's Conference in Brighton on 17 February, where WASPI will be represented.
A statement on the campaign's site said: "This truly is an amazing achievement and a fantastic example of women working in Unison."
WASPI director Susan Beevers said: "Though we've had support from trade unions on a local level, Unison's backing will help the consolidation of that support on a national level.
"WASPI group coordinators have self-funded their campaign activities and involvement so far, so this support will help us to be in a better financial position."
Beevers added: "Access to this database of members will help the WASPI campaign more easily reach out to women, particularly for those who are not on social media which has been big part of how we've comminucated so far."
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