Amidst high security for the wedding of William Windsor and Kate Middleton, the union was outside the gates of Buckingham Palace from 12 noon to 2pm on 28 April 2011 with a giant 'fair pay for royal cleaners' card for members of the public to sign.
An online petition has also been launched (http://www.pcs.org.uk/en/culture_media_and_sport_occupational_association/campaigns/fair-pay-for-royal-cleaners.cfm).
Cleaners in Buckingham Palace, St James's Palace and Clarence House who are paid just £6.45 an hour are campaigning for an increase to the 'London living wage' of £7.85 an hour.
The London living wage, introduced by previous Mayor of London Ken Livingstone and endorsed by current mayor Boris Johnson, is paid to cleaners in the houses of parliament.
The royal cleaners are employed by two private contractors, KGB Holdings and Greenzone, but the union believes ultimate responsibility rests with the Royal Household, which receives around £30 million a year from taxpayers - half of which is for upkeep of the occupied palaces.
PCS general secretary Mark Serwotka commented: "While the royals were preparing for the prince's lavish wedding, our members were and are being treated like paupers."
He added: "The royal family is seen as a major contributor to the tourist industry and many people visit London specifically to see the palaces. We'll be asking them to show their support for the people on poverty pay who keep these palaces clean."
The Public and Commercial Services union represents civil and public servants in central government. It has more than 300,000 members in over 200 departments and agencies, and in parts of government transferred to the private sector. PCS is the UK's sixth largest union and is affiliated to the TUC.
The online petition for a Living Wage for royal cleaners can be signed here: http://www.pcs.org.uk/en/culture_media_and_sport_occupational_association/campaigns/fair-pay-for-royal-cleaners.cfm