The Financial Services Authority has activated rarely-used powers to allow the Nationwide Building Society quickly to push through its mergers with the smaller Cheshire and Derbyshire building societies without seeking approval from their members.

The mergers, announced on Monday, will see both the Cheshire and the Derbyshire absorbed by the Nationwide by the end of the year, much faster than typical mergers between building societies. Both mergers are making use of special powers in the Building Societies Act that enable the FSA to approve a building society merger without a vote by members if the watchdog feels the deal is in their best interests.