The Ryder Cup golf tournament is "highly likely" to increase the number of women and children trafficked to Wales for the sex trade, it is claimed.
A report by assembly members said evidence from other countries suggested trafficking increased significantly for major sporting events.
They recommended setting up a new post of trafficking director to deal with the problem in Wales.
The Ryder Cup takes place at the Celtic Manor Resort, Newport from 1-3 October.
The Knowing No Boundaries report said: "Greece licensed a large number of additional brothels in the months leading up to the 2004 Olympic Games in Athens, and mega-brothels were installed near the German football stadia during the football World Cup in 2006.
"It is therefore highly likely that the Olympics as well as other major sporting events to be held in Wales, such as golf's Ryder Cup in Newport this October, will attract a significant increase in the number of women and children trafficked for the sex trade as demand increases."
The report said other countries' experiences illustrated the need to act "decisively and immediately" to combat human trafficking in Wales.
Evidence from Wales' 22 local authorities put the number of "proven" or "suspected" cases of human trafficking at 15.
However, the report's authors said this did not include a major city which described the issue of trafficking as "nothing new" and was "in all probability a significant underestimate".
The report said there was "a mixed picture" of local authority responses to the problem, with "a failure to address the situation of human trafficking effectively" in some cases.
Joyce Watson AM, chair of the cross-party working group, said trafficking was prevalent in every type of community in Wales
She said: "The common perception, particularly in rural Wales, is that human trafficking is something which happens elsewhere, far away from seemingly remote villages in the Welsh countryside.
"This perception is not only false, but impedes progress which could be made in tackling a crime which is hidden from society."
She said human trafficking was prevalent in every type of community in Wales, "from the urban streets of Cardiff to the rolling hills of Carmarthenshire".
The report's other recommendations included dedicated funding to tackle trafficking, a campaign to raise awareness of the problem, and specialised training for those on the "front line".
Jeff Farrar, Assistant Chief Constable of Gwent Police and all-Wales lead for police on protecting vulnerable people and human trafficking, said the report provided "a positive step forward in attempting to guage the scale of human trafficking in Wales".
He said: "To date much of this goes unreported as victims are often reluctant to report matters to the police or other agencies.
"There is already a single point of contact and senior officer in place in each of the four Welsh forces who is the dedicated work lead in the area of human trafficking."
He said that as a result of discussions - not in relation to the Ryder Cup - they recently met partner agencies including the Welsh Local Government Association, Barnardo's and the UK Human Trafficking Agency to share intelligence.
"Current intelligence across Wales does not indicate that human trafficking is widespread and there is no specific intelligence that indicates that any of the large sporting events in Wales including the forthcoming Ryder Cup have or will increase human trafficking," he said.
"However, the police like many other agencies are keen to work in partnership with assembly members to ensure we have an accurate picture of human trafficking in Wales to allow us to work together to protect these vulnerable people and bring to justice those responsible."
Newport council said it regarded the trafficking of women and children as a serious issue at any time, but had no reason "to expect this to become a more significant problem because the Ryder Cup is coming to Newport".