Patricia Kaliati says men are unable to love more than one wife equally
Muslims in Malawi have been angered by government plans to ban polygamy.
A spokesman for the Muslim Association of Malawi told the BBC the proposed law would discriminate against the country's Muslim minority.
He said with about 6% more women than men in Malawi, if polygamy were banned, many women would be left without a husband and become prostitutes.
The gender minister said the ban was necessary to prevent women from being abused in polygamous relationships.
She said problems occurred because men could not give their full attention to more than one woman.
"When a man has two, three, four wives, they are not co-operative - one will be the loved one," said Gender Minister Patricia Kaliati.
It had not been a hasty decision and there had been wide consultation about the matter, she said.
But Imran Shareef Muhammed - secretary general of the Muslim Association of Malawi - disputed this.
"The minister is lying - she didn't consult the Muslim community," he told the BBC's Network Africa programme.
"We are totally rejecting it. There are also other ethnic groups [who practise polygamy] and they also totally reject this," he said.
"If these people go ahead banning polygamous marriages it means many women will go into prostitution.
"Every woman has the right to be under the shelter of a man."
He said under Sharia law, polygamy was optional.
"I have only one wife, my dear wife... but the moment they proceed with this, I will take a second wife," he said.
Should the ban come into affect, those already in polygamous marriages would not be affected, but those who flout it could face imprisonment, the minister said.