Lawmakers say it would be the perfect wedding gift — changing Britain's rules of succession so any daughter born to Prince William and wife-to-be Kate Middleton would enjoy an equal right to the throne.

Britain's Prince William (R) and his fiancee Kate Middleton arrive at The Thursford Collection in Norfolk, England, Dec 18, 2010. [Agencies]?

Lawmaker Keith Vaz is leading a House of Commons debate Tuesday calling for an overhaul of the 300-year-old procedures.

The system currently gives sons an automatic preference over older female siblings to succeed to the British throne.

Vaz says William's April 29 wedding offers a once-in-a-generation chance to make the change, which has previously been discussed but never approved.

Any change must be authorized by every nation where Queen Elizabeth II is head of state.

Prime Minister David Cameron's office says reforms would be "complex and difficult."