Yorkshire Building Society members have voted in favour of a merger with the Chelsea Building Society, paving the way for the deal to go ahead.
Some 86.7% of savers and 85.4% of borrowers were in favour of the merger, which members of the Chelsea have already approved.
The two building societies agreed to merge in December.
It was widely considered a rescue for Chelsea, which in 2008 lost £44m it had invested in failed Icelandic banks.
The merger will complete on 1 April, subject to confirmation by the Financial Services Authority.
The deal would create a society with 2.7 million members, a network of 178 branches and assets of £35bn.
