The new law allows courts to stop forced marriages and provide protection to those who have been married against their will.
It also gives judges the power to require individuals to reveal the whereabouts of people thought to be at risk of being forced into marriage, stop potential victims from being taken abroad, and seize passports.
According to the Forced Marriage Unit (FMU), 65 percent of known cases of the practice involve Pakistan, where Miliband is set to visit on Wednesday.
The FMU also says that a quarter of forced marriage instances involve Bangladesh, with 85 percent of all victims being women and a third of victims under the age of 18.
Distinct from mutually-accepted arranged marriages, forced marriages have led to suicides and "honour killing" murders in Britain, shocking a nation widely deemed to have successfully absorbed immigrant cultures.
In a newspaper article Sunday, Miliband said Britain was taking a tougher stand against forced marriage, describing the practice as "a stain on those who carry it out, those who condone it and also those who ignore it."
He recounted the tale of British diplomats rescuing a 15-year-old girl last week from a village near Mirpur in northern Pakistan, where she was being held prisoner and beaten by her father to get her to agree to marriage.
So far this year, the FMU has handled more than 1,500 reports of forced marriage and diplomats across the world have helped more than 400 people facing possible forced marriage or being made to sponsor an immigration visa after marriage has taken place, Miliband said.
Under the new laws, those who do not comply with court orders related to forced marriage - which can be sought by a victim, a friend or the police - could face jail.
"This new law is a powerful tool that will help ensure that no-one is forced into marriage against their will and those already in such marriages will receive protection," junior justice minister Bridget Prentice said.
"Our policies reinforce that hope and send a clear message that we are committed to providing support and help to victims and that violence of any kind will not be tolerated."
A spokeswoman for the justice ministry acknowledged that while the "primary purpose of the act is preventative" the same protection will be made available to women already forced into marriage.
"Where a forced marriage has taken place, they (the courts) would also be able to make orders to protect the victim and help remove them from that situation," she said.
Shaminder Ubhi, director of the Ashiana Network, which works with victims of domestic violence, noted that while not everyone would want to use the legislation, "this act sends a clear message that forced marriage will not be tolerated and perpetrators will be held accountable."