As announced in Autumn 2013, the government are introducing legislation with effect from 2015/16 to allow a spouse or civil partner to transfer 10% of their unused personal allowance to their spouse or civil partner.
Transfer is only possible provided the transferor is not a higher rate taxpayer.
If one person in a couple doesn’t use their full personal allowance of £10,500 they can transfer £1,050 of their tax free allowance. It’s hard to see the justification for limiting the amount transferable and I hope that there may be scope for increasing this in future budgets.