Commonwealth leaders are expected to agree to amend legislation that gives male heirs priority in the line to the throne.
At the summit for Commonwealth countries in Australia yesterday, David Cameron called the 400-year rule "outdated and wrong". He sought approval from the other 15 "realms" where the Queen is head of state.
The Prime Minister said the marriage of the Duke and Duchess of Cambridge this year was the ideal spur to change the 400-year-old rule so that if their first child was a girl she could become queen.
Downing Street is also confident of securing support from Commonwealth leaders for scrapping the bar to the monarchy of anyone who marries a Catholic.
"These rules are outdated and need to change," Mr Cameron said before the opening of the bi-annual Commonwealth Heads of Government Meeting in Perth.
"The idea that a younger son should become monarch instead of an elder daughter simply because he is a man just isn't acceptable any more. Nor does it make any sense that a potential monarch can marry someone of any faith other than Catholic. The thinking behind these rules is wrong," said Mr Cameron.
Any change would require the agreement of all 16 Commonwealth realms.