Sir Steve Webb will join Lane Clark and Peacock (LCP) as a partner, leaving Royal London where he is currently director of policy.
The former pensions minister joins the consultancy to focus on its client service and the "ever-evolving" regulatory environment.
Joining on 10 February, he will also spearhead LCP's campaigns to help keep the wider industry apace with change and member needs.
It comes after the consultancy last year appointed its first chief executive, Aaron Punwani, as part of a wider management structure shake-up designed to support growth and innovation.
The firm posted record income of £115m, an 8.5% increase on the previous financial year.
Webb said: "I have known and worked with several people from LCP over the years and I know that the firm places great emphasis on client care and creating a working environment that enables talent to flourish.
"Their people-centred ethos means that the needs of pension scheme members is always uppermost in the work they do. After four happy and productive years at Royal London working with some great people, I can't think of a better place for my next move, especially as LCP is experiencing an exciting period of growth."
Punwani added: "Steve Webb was not only the UK's longest-serving pensions minister, but also the most highly regarded pensions politician the UK has known in recent times.
"He continues to be widely respectively throughout our industry and across the political party spectrum.
"Steve's insight will help LCP to shape the future of the pensions industry and to adapt our services to meet the future needs of our clients."
Webb was pensions minister between 2010 and 2015 under the Conservative and Liberal Democrats coalition government.
He left office after losing his Thornbury and Yate seat, which he had held since 2010, having previously been MP for Northavon since 1997.
This article originally appeared on our sister title Professional Pensions.