The mininum age to get married could be changed to 18 to stop forced marriages, but the age of consent would not change with it.
Sajid Javid MP will introduce a private member's bill next week that will make it illegal for anyone to marry below the age of 18 in England and Wales.
Currently,16 and 17 year olds can marry with their parents' consent but it is feared that this permits forced marriages on some girls.
Javid's bill is suspected to pass as it has widespread support in the Government and across the parties to close the loophole.
However, there is no plan to change the age at which someone can consent to sex, meaning 16 and 17 year olds will legally be allowed to have sex but not get married.
One pastor, Stephen Kneale, commented online: "So you can't marry until 18 (which is probably sensible) but the age of consent remains 16. The former home secretary can say marrying at 16, as a child, is abuse but no comment on having sex at 16, as a child, which implicitly suggests that isn't.
"In my view, we would do well to standardise most things at 18, when we recognise people as legal adults. Smoking, drinking, voting and now marriage are all limited (imo rightly) to adulthood. Strikes me the age of consent ought to follow suit."
Theology Professor John Milbank wrote on Twitter: "Will the churches say anything about this? About the first legal suggestion that rights to have sex do not imply also rights to marry? As if sex and marriage had nothing to do with each other. Will they say anything about such an assault on primordial human liberty?"
Campaigners against child brides also want to see those involved in arranging child marriages treated more harshly.