After Commonwealth leaders agreed to reform succession laws, sons and daughters of any future UK monarch will have equal rights to the throne, according to British Prime Minister David Cameron.

At a Commonwealth of Nations conference in Australia, the leaders of the 16 Commonwealth countries with the queen as head of state unanimously endorsed the reforms, he added. For the amendments to take effect, the individual governments of those 16 nations must still agree.

Before the next general election, the prime minister will draft legislation in the United Kingdom to guarantee that the reforms apply to any offspring of the Duke and Duchess of Cambridge. According to officials, the changes will take effect even if a child is born before the new laws is enacted.

It implies that the Duke and Duchess of Cambridge’s first-born daughter will take priority over younger boys.

The monarch’s marriage to a Roman Catholic was likewise permitted.

Cameron praised Friday’s agreement by the heads of government of the 16 nations as “something of a historic moment” when speaking beside his Australian colleague Julia Gillard in Perth.

In a televised speech, he stated that attitudes have evolved significantly over the ages, and that obsolete policies should change with them.

“The idea that a younger son should become monarch instead of an elder daughter simply because he is a man, or that a future monarch can marry someone of any faith except a Catholic — this way of thinking is at odds with the modern countries that we have become,” he added.

“Put simply, if the Duke and Duchess of Cambridge were to have a little girl, that girl would one day be our queen.”

“These rules are outdated and need to change,” Cameron said before the start of the Commonwealth heads of government conference in Perth, where the agreement will be inked.

According to the old succession laws, which date back more than 300 years, the successor to the throne is the monarch’s first-born son. Only when there are no boys, as in the case of the Queen’s father, George VI, does the oldest daughter inherit the throne.

Speaking to CNN, royal expert and former International Who’s Who editor Richard Fitzwilliams, said the adjustments are critical if the monarchy is to adapt to changing circumstances.

He stated that “for decades, since the 1950s, there’s been talk of doing this and nothing’s actually happened,” most likely due to the fact that it did not impact Prince Charles, Prince William, and Prince Harry.

“Now the Duke and Duchess of Cambridge have said they want to start a family, this makes it urgent,” he remarked.

Cameron said: “The idea that a younger son should become monarch instead of an elder daughter, simply because he is a man, just is not 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. That’s why people have been talking about changing them for some time. We need to get on and do it.”

Australia’s Prime Minister, Julia Gillard, described the occasion as “extraordinary”: “I’m very enthusiastic about it. You would expect the first Australian woman prime minister to be very enthusiastic about a change which equals equality for women in a new area.”

She stated that the adjustments looked to be straightforward. “But just because they seem straightforward to our modern minds doesn’t mean that we should underestimate their historical significance, changing as they will for all time the way in which the monarchy works and changing its history.”