If a husband and wife own a property jointly, for rental income purposes, by default, half the income is attributed to him, and half to her.
Unless the rental property it is actually owned in a different proportion than 50:50 and this is evidenced by the ownership deeds of the property, then the income received should always be as a half share to the husband and a half share to the wife.
If you wish for your wife to take advantage of her personal allowances and lower rates of tax by receiving more of the rental income, you will need to make her owner of the property in the proportion that you wish to declare the rental income.
For example, if you wish for 90% of the rental income to be declared by your wife, you must make her a 90% owner of the property by changing the ownership deeds, and advising the HMRC of the different ownership proportions.
You will also need to consider the Capital Gains Tax and Stamp Duty Land Tax implications of transfer, and should therefore always take advice from a solicitor and local TaxAssist accountant before proceeding.