LONDON -- Britain is to increase the age at which foreigners can apply for a marriage visa to crack down on forced marriages, the government said Wednesday.

The age of sponsorship will be upped from the current 18 to 21, the Home Office said, outlining proposals aimed at strengthening the safeguards against the practice.

The government's Forced Marriage Unit dealt with 69 cases of overseas forced marriage in 2007 involving young people aged 18 to 21 -- about 30 percent of its workload.

"Forced marriage leads to victims suffering years of physical and mental abuse and -- in extreme cases -- unlawful imprisonment and rape," Home Secretary Jacqui Smith said in a statement.

"It has no place in our society. That is why the government is determined to do everything it can to stamp it out and to ensure that victims receive the help and support they need."

Other measures announced Wednesday include asking foreign spouses to agree to learn English before coming to Britain and a new power to revoke leave to remain if the marriage is found to be forced.

Any British citizen applying to "sponsor" someone to come to Britain as their spouse will have to declare their intention before they leave and marry abroad.

Border and Immigration Minister Liam Byrne said: "British citizens have the right to marry whoever they choose. But we want newcomers to succeed in our society and sign up to the standards we have in common.

"That means freedom, not being forced to marry someone, and it means newcomers quickly acquiring a command of English, with consequences for those who break the rules."

A national helpline for forced marriage and "honour" crime victims was launched here in April, run by a charity but backed by the government, which is concerned about the scale of the problem among people of south Asian origin.

The Forced Marriage Unit deals with 300 cases of forced marriage a year, but believes the true figure could be up to 4,000.