Spain's far-right Vaux Party on Monday's refusal to sign a party-wide declaration condemning violence against women has sparked outrage among civil rights groups and embarrassed allies of the Conservative Party.

Vox's refusal to sign a statement from the Madrid City Council means that for the first time since a landmark gender violence law in 2004, local authorities in the Spanish capital were unable to issue a joint statement.

This month's election has made Vaux the third largest party in the Spanish parliament, after more than doubling its mix of nationalist, anti-Muslim and anti-feminist speech.

Javier Ortega Smith, a member of the Madrid City and National Assembly, said that on the United Nations International Day to Eliminate Violence against Women, the declaration addresses only one side of gender-based violence.