The number of girls forced into marriage amongst Syrian refugees has tripled since the conflict began, organisation CARE says.

They report that threats of sexual violence in refugee camps has prompted some families to sell their daughters in case they are raped and no longer considered "honourable".

CARE also found that worldwide, there is a new child bride every two seconds, with African countries topping the list.

"We're seeing a massive increase in child marriage," said Isadora Quay, a Gender in Emergencies Specialist from CARE.

"Child marriage was a factor of life — child marriage being marriage of people under 18 — was something that did happen but much rarer in the past than it is today.

"So we've seen a massive increase in child marriage in Syria and in Iraq, and we've seen even as far afield as places like Egypt.

"Syrian refugees have been talking about the concept that Syrian girls are being offered up for child marriage and that they are very much in demand as child brides."

Ms Quay said child marriage was being used as a weapon of panic to displace populations.

She recently spoke with women in refugee camps in Turkey, who raised it as one of the most serious issues they were facing.

"It was really interesting, I did interviews with both men and with women separately," she said.

"For the women's group, the first thing that they said was, 'we're really concerned about child marriage' - or 'early marriage' as they called it - 'we're really worried about our daughters, our cousins, our sisters being married off early.'

"It was the first thing they mentioned.

"We had the same set of interviews with men and they didn't mention it at all.

"In fact it was only when I asked them about it that they said, 'oh yes, that's a problem.'

According to the organisation, between 2011 and 2014 the number of forced marriages in the Syrian refugee population in Jordan trebled for girls aged 15 to 17.

Forced marriage 'devastating', linked to life of poverty

Associate Professor Rita Shackel from the University of Sydney said forced marriage had serious life-long implications.

"The impact can be hugely significant and in many cases devastating for the young girl," she said.

"Unfortunately the research in this area shows forced marriages on young girls have lifelong impact.

"It's very much tied into lack of access to education moving forward in their life, and also is linked to being trapped in a life of poverty."

Australia was preparing to take on 12,000 extra Syrian refugees but it was unclear if the nation's laws could protect those who were forced into marriage before they arrived.

"I think that raises a whole host of legal complexities," Professor Shackel said.

"I think what's important about the laws that we have in Australia is that if someone who is living in Australia is actually taken overseas to a forced marriage, then those laws apply and the penalties that are attached to that criminal conduct is quite severe.

"It's actually more severe than being a part of a forced marriage in an Australian context."

The ABC has asked the Department of Immigration and Border Protection for clarification about its policy surrounding refugees who are victims of or participated in forced marriage.