Gordon Brown is in talks with Buckingham Palace to reform laws relating to succession of the throne. The aim is to end the centuries-old rule which gives men priority over their elder sisters, and review the ban on members of the royal family marrying Roman Catholics.
The PM plans to raise the ideas, which he says are supported by public opinion, at the Commonwealth summit in November, as the 1701 Act of Settlement affects every country where the Queen is head of state.
"This is not an easy set of answers, but I think in the 21st century people do expect discrimination to be removed and they expect us to be looking at these issues," says Mr Brown.
If the legislation is updated it would lead to Princess Anne rising from tenth-in-line to fourth, bypassing Princes Andrew and Edward and their children. The new law would also have particular significance should Prince William's first child be a girl.
The religious issue has also come to the fore recently. In order that Peter Phillips retain his place as 11th-in-line, Autumn Kelly gave up her Catholic faith before becoming his wife. The planned revisions would mean this would no longer be necessary.