A 14-year-old girl was forced to marry a man 20 years her senior in a Melbourne mosque, a court has heard.

In video footage of the ceremony, the young teenager can be seen dressed in a light-blue headscarf in a tiny room hidden at the back of the suburban mosque as she waits in silence to be married to a man she has reportedly known for just a few days.

The ceremony took place last September but the film has come to light amid a dramatic increase in reports of forced underage marriages in Australia in the past few years.

Mohammad Shakir, now 35, sobbed in court as he pleaded guilty to going through a formal ceremony of marriage with a person not of marriageable age at Noble Park mosque last September.

Australian network 7 News obtained the footage and reported the young bride was handed over for marriage by her parents in return for a AUD$1480 gold necklace.

The child’s mother watches on as the ceremony takes place, with the man conducting the ceremony asking the girl: “Do you take (this man) to live together and live according to Islam?”

“Yes,” she responds quietly.

“As a wife, you have a duty to obey your husband,” the Imam tells the child bride after the ceremony as the groom signs papers.

The footage was found on the groom’s phone by police who arrested both him and the Imam, named as Ibrahim Omerdic, who performed the ceremony when he was leader of the Bosnian Islamic Society and Noble Park Mosque.

As part of groom Shakir's plea, two charges against him that he had sex with the girl after the ceremony were withdrawn.

Shakir, who spent six months in prison awaiting the court case, shed tears after entering his plea during what was to be a pre-trial committal hearing, according to Australian media. The case was adjourned until September.

He was helped in court by a Burmese interpreter.

The teenager, who was in court, also wiped tears from her eyes.

Mr Omerdic, 61, also appeared at Melbourne Magistrates’ Court charged with conduct that caused a minor to enter into a forced marriage.

He was sacked after he was arrested in November and his marriage licence was revoked. His barrister said the defence will contest whether there was a marriage and whether there was any intention to perform a marriage ceremony.

Between December 2014 and January 2017, there were reports of 57 child brides in Australia, where the legal age for marriage is 18. The marriage of a person aged 16 or 17 where the other person is aged 18 or over is considered only in “unusual and exceptional” circumstances.

Of these children, 34 were aged 16-17, 12 were aged 14-15, seven were aged between ten and 13, while four were under the age of 10. The majority of these offences took place in the Sydney area.

In the past two years, the child welfare group, Plan International Australia, identified another 250 cases of underage marriage across Australia.

Because the offence of underage marriage was not criminalised until 2013, police cannot prosecute for instances which took place before then. However, the number of cases being investigated by Federal Police doubled in the past year to 69.

The penalty for forcing a child into marriage is up to 25 years in prison. Such unions have no validity in law and are mostly kept hidden.

Pru Goward, the Australian Government’s Family and Community Services minister, told the Australian network: “It is deeply disturbing to think of little girls, pre-puberty, being considered for marriage and for people to be organising that marriage.”

Laura Vidal of The Freedom Partnership, which works to end modern slavery in Australia, said: “The long-term impacts of people being forced into marriage can be quite serious, including forced or unwanted pregnancies (and) withdrawal from education.”

The Board of Imams in Victoria issued a statement against forced and child marriages.

"Underage marriages are illegal in Australia. As Australian Muslims, we are required to observe and respect the laws of Australia," the statement said.

The statement added that imams should meet both the bride and groom in person before the marriage ceremony to ensure they are of marriageable age and both consented.

Forced marriage including underage marriage is also on the rise in the UK according to figures released jointly by the Home and Foreign Office.

Statistics revealed a 17 per cent increase in the number of children believed to have been forced into marriage, usually with a much older man, between 2015 and 2016.

In 2016, the Forced Marriages Unit in the UK gave advice or support related to possible forced marriages in 1,428 cases, with 26 per cent of these involving victims below the age of 18.