New laws to modernise the rules of succession to the throne have been backed by MPs despite warnings of "unwanted, unintended consequences".
Deputy Prime Minister Nick Clegg said the current rules, which discriminate against women and ban royal heirs from marrying Roman Catholics, were from a "bygone age" and sent out the wrong message about modern Britain.
The changes will mean the Duke and Duchess of Cambridge's first child, expected in July, can become monarch even if it is a girl who later has younger brothers.
The legislation, which is being rushed through the Commons with just two days of consideration by MPs, was given an unopposed second reading.
But a number of MPs raised concerns about the way the Bill was being pushed through the House and there were also questions about whether children of a royal who married a Roman Catholic would be brought up in the church, therefore losing their place in the line of succession as Catholics remain barred from the throne.
Tory Jacob Rees-Mogg, MP for NE Somerset, said the Bill was being "treated as if it was terrorism legislation" and it was an "insult to the nation and to our sovereign and indeed to Parliament".
The Prince of Wales has reportedly expressed concerns about the Bill and his friend Tory MP Nicholas Soames warned of the "unwanted, unintended consequences that often flow from tinkering with legislation of this type and could damage the crucial relationship between church and state, as well as peerage law and quite possibly interfere with accepted conventions and laws reaching back down the times".
Mr Soames said the Government was acting "out of consideration ... of political correctness on one hand and the European Convention on Human Rights on the other".
He dismissed the Bill as coming from the "good wheeze school of Government, a doctrine much in fashion which does not receive nearly rigorous or formidable enough scrutiny".
The legislation also replaces the 1772 Royal Marriages Act which requires descendants of George II to seek the reigning monarch's consent before marrying, without which the union is void. Instead, the first six royals in the line of succession will require the monarch's consent for their marriage.