Turkey's government wants to make adultery a crime, the justice minister has been quoted as saying -- a proposal that has outraged the main opposition and women's groups.
Although the legislation would also apply to men, a previous adultery law abolished six years ago was used mainly against women.
The ruling Justice and Development Party (AKP), which traces its roots to a banned Islamist movement, wants to include the adultery ban in an overhaul of the penal code, promised as part of reforms aimed at meeting European Union criteria.
The main opposition party has threatened to vote against the entire penal code reform if the clause on adultery is included in the bill and brought to parliament.
"We believe that adultery should be a crime, because society also expects this," Justice Minister Cemil Cicek was quoted as saying by newspapers on Monday.
Turkey's top court struck down a law penalising adultery in 1998 and said in its ruling that the law had been mainly used against women, leading to gender inequality.
Although Muslim Turkey has enshrined equality for women, rights groups say discrimination against women remains endemic.
The EU is expected to criticise the lack of equality for women in Turkey in a progress report on the country's candidacy due in October, diplomats have said.
The penal code's other reforms aim primarily to expand rights to meet the EU's basic criteria for membership. Turkey is hoping a swathe of recent rights reforms will convince Brussels to set a date to begin accession talks next year.