Downing Street has warned that any attempt to change the 309-year-old law governing the royal succession would be a “difficult and complex matter”.
MPs are to debate a motion by Labour backbencher Keith Vaz calling for an end to the rule of “primogeniture” which means that sons succeed to the throne ahead of daughters.
Mr Vaz, chairman of the Commons Home Affairs Committee, is expected to argue that if Prince William and Kate Middleton’s first child is a girl, she should succeed ahead of any boys who may follow.
His motion, to be debated under the 10-minute rule procedure, calls for legislation to “remove any distinction between the sexes in determining the succession to the Crown”.
In practice, there is no prospect of amending the law without the support of the Government.
But while the Prime Minister’s official spokesman acknowledged that elements of the 1701 Act of Succession – which also bars Roman Catholics from succeeding to the throne – are “discriminatory”, he played down the prospects of change.
“Amending the Act of Succession is a complex and difficult matter that requires careful and thoughtful consideration,” the spokesman said.
One problem which has confounded previous moves to reform the Act is that change would require parallel legislation in all the other Commonwealth nations of which the Queen is head of state.
Talks among the countries concerned have been ongoing for some time.
The Prime Minister’s spokesman confirmed that they are still continuing but said that it would “not be appropriate” to release any details.