As a result of a government pay freeze and pension policy, real-term earnings have decreased by 20% since the government came into power in 2010.
PSI has sent a letter of solidarity and support to its affiliate unions whose members were on strike.
Unison general secretary Dave Prentis said: "These workers care for our elderly, clean our streets, feed and educate our school children and keep our libraries running, but they receive no recognition in their pay packets.
"They are mainly low-paid women workers, stressed and demoralised, and they deserve better from their employers and from this government.
"This is the group that has borne the brunt of the government's austerity agenda."
GMB national officer Brian Strutton said: "GMB members serving school meals, cleaning streets, emptying bins, looking after the elderly, helping children in classrooms and in all the other vital roles serving our communities are fed-up with being ignored and undervalued."
He added: "Their pay has gone up only 1% since 2010 and in October even the national minimum wage will overtake local authority pay scales.
PCS general secretary Mark Serwotka said: "Ministers praise public servants for their hard work and dedication but at the same time they are slashing their living standards. Instead of warm words, public sector workers need a pay rise.
"As politicians of all parties justify pay cuts by repeating the lie that there's no money around, and household incomes fall to their lowest for more than a decade, it is clear the so called economic recovery is not being felt by everyone."
Fire Brigades Union general secretary Matt Wrack said: "The FBU has wanted to settle our dispute for a long time, but the government at Westminster is simply not listening. We are therefore proud to take strike action alongside our colleagues in other unions on 10 July.
"The fact that this government has united so many workers to take strike action against them is a testament to the failure of their policies. They are destroying our public services and wrecking the lives of millions.
Unite national officer for local government Fiona Farmer said: “Our members have endured four years of pay cuts in real terms and they have now voted overwhelmingly to strike on 10 July to drive home the message to ministers that ‘poverty pay’ in local government must end.
“Poverty pay is widespread across local councils – household bills continue to soar, but our members’ buying power is constantly being eroded. The national minimum wage will soon overtake local government pay scales; members are choosing between heating and eating.
“For too long the council workers have been targeted to bear the brunt of the austerity measures that have been imposed by millionaire cabinet ministers since 2010.
“The aim is to get the employers back around the table to negotiate a fair deal for those who deliver vital local government services, from social care to refuse collection, on a daily basis.”
The national trade union organisation TUC has also organised a mass protest on 18 October in London, with other protests organised around the UK.