Yorkshire and Britannia share a common philosophy

David Anderson, Yorkshire chief executive

The two societies say they intend to remain independent, although they will look at other ways of working together.

The UK's building societies have declined in number in recent years, as members have voted for them to convert into stockmarket-listed banks, or to be bought by banks.

Building societies are mutually owned by their members - meaning that such changes in status has led to members pocketing windfalls.

Mutual status

The remaining building societies, led by the Nationwide, the biggest, have been taking a range of measures to defend themselves against such conversion votes.

Britannia and Yorkshire will be hoping that their initiative will help persuade members to stick with mutual status.

Work has already begun on making their computer systems compatible.

Britannia, with 2.2 million members and 190 branches is the UK's second biggest building society.

Yorkshire, with 1.8 million members and 132 branches, is the third largest.

'Better value'

Members of each society will be able to pay in or withdraw money free of charge from the other society's branches.

Britannia chief executive Graham Stow said: "At a stroke we will significantly expand our network without adding to our costs, providing real added value to our members."

David Anderson, chief executive of Yorkshire Building Society, said: "Yorkshire and Britannia share a common philosophy - that being mutually owned allows us to provide better value and services to our members."