Many online have criticised his comments for endorsing the idea that girls as young as 12 can give consent.
In Zimbabwe, 4% of girls marry by the age of 15 and 30% by 18, the UN says.
Information Minister Jonathan Moyo joined the criticism, calling Mr Tomana's interview "outrageous", and suggesting that his comments compromised his position as prosecutor general, in a post on twitter.
The wishes of girls who want to get married early and who give their consent to under-age sex should be considered carefully, Mr Tomana said.
The current legal age of consent in Zimbabwe is 16.
Recent cases in which convicted rapists had their sentences suspended have created a growing public debate over the level of legal protection being offered to young girls, reports the BBC's Steve Vickers from the capital Harare.
There have been cases of young girls consenting to sex after being offered sweets or small amounts of money, sometimes as little as a dollar, our reporter says.
There is also a grey area being created by the amount of discretion judges are allowed in interpreting the law, he adds.
"My 12-year-old is a baby; she can't even tie her own shoelaces, so how does she consent to sex," one mother in Harare told the BBC's Focus on Africa radio programme.
Mr Tomana also supported the practice of sending convicted child sex offenders to do community service in schools, saying that they were "no longer a threat to anyone".
Source: bbc news
