Marg Dean said the shocking statistic, which included current and historic sexual assaults, was rising every year.

She estimated just one in 10 victims, who were mainly women, were reporting the assaults to police.

Women's Legal Service managing solicitor Susan Fahey said she was not surprised by the number of victims or the lack of reporting.

"One in four people will be sexually assaulted in their lifetime, 30 a month is not a shock," Ms Fahey said.

"They are really scared about how they are going to be treated by the system ... so they go somewhere like Laurel House and the police aren't involved."

While Tasmania Police does not have a specialised sex crimes unit Assistant Commissioner Donna Adams said officers were trained to assist sexual assault victims when they made a report.

"Tasmania Police takes all assaults, including sexual assault, very seriously and it is a concern that assaults do go unreported," she said.

"We encourage the victim of any assault to report the matter to police for investigation."

Human Services Minister Cassy O'Connor, whose portfolio includes women's issues, said she was "deeply disturbed" that victims felt they could not report sexual assaults.

Ms Fahey said some victims might not realise what had occurred was actually deemed sexual assault or might see it as typical of domestic violence.

Ms Dean also linked victims knowing their offenders to the lack of reporting.

"If disclosed the offender will be isolated from family, friends, peers. Also offender tactics isolate victims from support networks (and) victims don't know what to do or where to go," Ms Dean said.

According to police the number of sexual assaults recorded in 2011-12 decreased 35 per cent to 165 offences.

Laurel House provides support services in the North and North- West and the Sexual Assault Support Service provides services in the South.

They can all be contacted 24 hours a day. The Northern service can be contacted on 63342740.