A law comes into effect on Monday that raises the legal age of marriage to 18.
Even with parental consent, 16 and 17-year-olds can no longer marry or enter a civil partnership in England or Wales in an attempt to better protect children from forced marriage.
Under the Marriage and Civil Partnership (Minimum Age) Act, it is now a crime to arrange for children to marry under any circumstances.
The law will cover non-legally binding “traditional” ceremonies, which would still be viewed as marriages by the couple and their families, the government said.
Natasha Rattu, director of the Karma Nirvana charity, which is a member of the Girls not Brides Coalition, said she hoped there would be better identification and reporting of underage weddings.
“It is a huge leap forward to tackling this usually hidden abuse and will provide a greater degree of protection to those at risk," Ms Rattu said.
"We hope that the new law will help to increase identification and reporting, affording greater protection to children at risk.”
The government’s forced marriage unit provided advice or support in 118 cases involving people aged under 18 in 2021.
The Ministry of Justice said the statistics showed forced marriage is more likely to affect girls than boys, with 2018 figures for England and Wales showing that 28 boys married under the age of 18, compared with 119 girls.
Justice Secretary Dominic Raab said anyone found guilty of arranging child marriages could be given a sentence of up to seven years in prison.
“This law will better protect vulnerable young people by cracking down on forced marriage in our society," Mr Raab said.
“Those who act to manipulate children into marrying underage will now rightly face the full force of the law.”
Conservative MP Pauline Latham, who introduced the Bill in Parliament in 2021, said Monday was a “landmark day for the campaigners who have worked relentlessly for over five years to ban child marriage in this country”.
“Child marriage destroys lives and through this legislation we will protect millions of boys and girls over the coming years from this scourge," Ms Latham said.
Safeguarding Minister Sarah Dines said the government was working to ensure that training and guidance is provided to equip police, social workers and other frontline professionals to support and protect victims.
