British Prime Minister Theresa May on Wednesday said a decision by Russia to decriminalise some forms of domestic violence was a step backwards.

"We see this as a retrograde step by the Russian government. Repealing existing legislation sends out absolutely the wrong message on what is a global problem," May told parliament.

On Tuesday, Russian President Vladimir Putin signed into law a controversial bill reducing the penalty for violence against family members when it is the first such offence and does not cause serious injury.

It reclassifies such offences as administrative misdemeanours punishable by a fine.

Previously such action was defined as battery, and was punishable by up to two years in jail.

The move sparked rare protest in Russia and critics said it would exacerbate the already-widespread problem of domestic abuse of women by making it even harder for victims to get help through the legal system.

According to the state statistics agency, in 2015 there were 49,579 crimes involving violence in the family, of which 35,899 involved violence against a woman.

In January, rights group appealed to Russia's parliament not to pass the bill.

Amnesty International condemned it as a "sickening attempt to trivialise domestic violence".

Foreign affairs committee chief Konstantin Kosachev said the West was criticising the measure with the aim "of attacking our country". afp