Singapore has in recent years gradually eased social restrictions that have given it a straight-laced reputation.
But while the Bill takes a softer line on heterosexual sex, a ban on acts of “gross indecency” between males will remain.
Gay rights activists have said authorities have not laid charges under the section in recent years, even though it remains in force.
Vivian Balakrishnan, Singapore's Second Minister for Information, Communications and the Arts, said earlier this year that the city-state was undergoing liberalisation while retaining a very strong conservative core.
Although prostitution itself is not an offence in Singapore, the Bill would make it an offence to obtain commercial sex with a person under 18.
Conviction could lead to a prison term of up to seven years, while communicating for such a purpose could bring up to two years in jail, the Bill says.
Similar offences committed abroad would attract the same punishments, it said.
Local media have reported that some Singaporeans travel to the nearby Indonesian island of Batam for sex with teenage girls.
In another new provision, making travel arrangements intended to facilitate under-age commercial sex abroad would bring up to 10 years in prison, the Bill says.
The revised penal code, still to be passed into law by parliament, also broadens the scope of an offence against unlawful assembly.
An assembly of five or more people would be illegal if the group's common objective is to commit “any offence,” the Bill says, broadening the definition from mischief and trespass.
Singapore's laws against unlawful assembly gained prominence during last year's meetings in the city-state by the International Monetary Fund and World Bank.
Pro-democracy activist Chee Soon Juan engaged in a three-day standoff with police, who stopped him and a small group of followers from marching to the meeting venue after police rejected his application for a permit.
Leong Wee Keat , Todayonline
THEY are the most vulnerable to sexual perverts, and soon, under the Penal Code revisions, children will gain greater protection.
For one, sexual grooming — in which an adult befriends and establishes emotional control over a child, paving the way for sexual abuse or rape — will be outlawed.
Such a provision, which has been adopted in various forms by countries such as Britain, Australia and Canada, will "deter sexual predators who prowl the Internet for the purpose of sexual grooming of minors under 16", said the Ministry of Home Affairs (MHA).
For the offence of sexual grooming to be made out, there must have been prior meeting or communication, which can take place here or even abroad, on at least two occasions.
The alleged offender must also meet the victim with the intent to commit a sexual offence.
Noting an increase in Internet usage among minors here, Singapore Children's Society executive director Alfred Tan said the new law was the perfect complement to preventive measures adopted by parents, counsellors and teachers.
"It would make all perpetrators think twice," he added.
Lawyer Tan Hee Joek, an associate director at law firm Drew and Napier, agreed.
However, the former deputy public prosecutor noted that it might not be easy to prove this new offence as the cases could involve oral communication, or the sexual predator might be savvy enough to use language that does not suggest intent.
"The new offence may be of more value for its potential deterrent effect, since it warns possible predators that the law is stricter when it relates to younger offenders in such cir*****stances. Hopefully, that alone will deter them from even thinking of doing it," said Mr Tan.
Oral and anal sex with minors under the age of 16, though consensual, will be outlawed with stiffer penalties. Prostitution of a minor under the age of 18 will also be made a specific offence.
Women, too, will get greater protection. Husbands can no longer plead marital immunity under six cir*****stances, if they are charged with raping their spouses.
Some of the cir*****stances include: If a couple is waiting for their divorce to be finalised; if a woman has taken out a court injunction to restrain her husband from having sex with her; or if a woman has taken out a protection order against her husband.
The MHA described this as "a calibrated approach" since total abolition of marital immunity would be "too radical a step" and "may change the whole complexion of marriage in our society".
Association of Women for Action and Research president Constance Singam had hoped the Government would do away with the qualifiers, saying: "Rape is an act of violence committed against another person, no matter the cir*****stances."