In Government the Liberal Democrats introduced the Triple Lock on pensions. This policy was a pledge of the Lib Dems in 2010 and, despite being outnumbered 6:1 by the Conservatives, they introduced it (as well as 75% of all other Lib Dem policies from their manifesto).
The Triple Lock ensures that pensions always increase by either the cost of living, average earnings, or 2.5% (whichever is highest). This means that people relying on a pension will never lose out.
The Lib Dems have promised to keep the Triple Lock but the Conservatives have repeatedly refused to do the same.