The voluntary sector is "neglecting" the people who clean its offices, according to the organiser of the Living Wage Campaign.
Greenpeace, Friends of the Earth and NCH are among charities attending an event next month designed to address the "poverty pay" of contracted cleaners in the sector.
They will be encouraged to sign up as 'living wage employers', alongside Acevo, the Big Issue and the Institute for Public Policy Research, all of which already support the campaign.
Companies that have already signed up will be eligible for the Living Wage Employer award, brainchild of Matthew Bolton, social entrepreneur and organiser of the campaign.
The event, hosted by UnLtd, will be held on 18 May in London.