She will also say that people who knowingly pay illegally trafficked women for sex could face rape charges.
Ms Smith is to promise that more kerb-crawlers will be prosecuted and police will get powers to close brothels.
Buying or selling sex is legal but many prostitution-related activities, such as soliciting and pimping, are not.
Ms Smith said the government had considered banning paying for sex altogether but had ruled this out as there was no public support for such a move.
Instead, the government’s efforts will be focused on reducing demand for trafficked women and she said there would be a marketing campaign aimed at men who used prostitutes.
She told BBC Radio 4’s Today programme: “My proposal is that men should think twice about paying for sex. The reason they should do that is actually the majority of women don’t want to be involved in prostitution.”
She added: “Trafficked women don’t have a choice, men do”.
But Nikki Adams, of the English Collective of Prostitutes, said the government had “made up” the number of women being trafficked into the UK and most prostitution was “consenting sex”.
Under the plan, the Home Office is planning to criminalize paying for sex with a woman “controlled for another person’s gain”.
Those convicted would get a fine and a criminal record.
Pleading ignorance of the circumstances under which a prostitute is working will not count as a defense.
Under the plans, people who pay a prostitute for sex knowing they have been trafficked against their will could be charged with rape.
Ms Smith will promise that kerb-crawling will be punishable the first time a person is caught doing it, rather than just persistent offenders.
The Home Office said police would get powers to close brothels.
Currently they can only shut premises associated with prostitution if anti-social behavior or when Class A drugs are involved.
Critics of the government’s proposals say they will simply drive customers elsewhere, rather than tackling the problem.
Under the Home Office plans, lap dancing clubs would be subjected to the same licensing laws as sex shops, rather than as pubs and bars as at present.
This would allow people living nearby more chance to raise objections.
The Sexual Offenses Act 2003 made it illegal to buy sex from anyone aged under 18 and introduced penalties for trafficking adults and children for the purposes of sexual exploitation.
It is not illegal for someone aged over 18 to work as a prostitute in off-street premises but where there is more than one prostitute, the owner of the premises can be prosecuted for keeping a brothel.
Many of the activities associated with street prostitution, such as soliciting and kerb-crawling, are also illegal and it is against the law to advertise sexual services on cards in telephone boxes.
In December last year, Women’s Minister Harriet Harman said paying for sex should be outlawed.
BBC NEWS, 19 November 2008