Prison officers have called off protest meetings in the face of a threatened injunction to force them to return to work.

The Prison Officers Association claimed that more than 80% of its members had supported the stoppages, which appeared to contravene a ban on strikes by prison staff. "This has been a great success in raising the public's awareness to the inherent dangers that the coalition government's policy change will bring to the prison service in the future," said a spokesman.

Steve Gillan, the association's general secretary, said the organisation had been warned by the Treasury solicitor that ministers considered the protest meetings tantamount to industrial action and would seek an injunction if they continued.

The prisoners at the jails affected were put on a "lockdown" regime, but Gillan said minimum cover arrangements were in place to ensure prisoner safety.

Echoing concerns among public sector workers who staged a national walkout over pension reforms on Thursday, the POA is unhappy about plans to link the normal pension age for prison officers to the state retirement age. "The state pension age will ultimately rise to 68 and it is unrealistic to expect 68-year-olds to walk landings and grapple with prisoners aged 20 or 21," said Gillan.

The unofficial protests took place during a day of action by public sector workers including police officers, immigration officers, lecturers and NHS staff. Around 20,000 police officers marched in central London against proposed pay reforms and job cuts, while trade union leaders held a rally in Westminster to mark a national strike against public sector pension reform by five unions: the Public and Commercial Services (PCS) civil servants' union; health workers from the Unite union; teachers and lecturers from the University and College Union; the Nipsa civil servants' union in Northern Ireland; and Royal Navy support staff at the RMT union. The PCS claimed support for the strikes among members had been "very strong".

Mark Serwotka, the PCS general secretary, said members' pensions were being "robbed" by changes that include higher contributions and raising the public sector pension age. The government played down the impact of the stoppages, saying 100,000 civil servants had stayed at home compared with 146,000 in the previous national day of action on 30 November last year, when other civil service unions took part. The Cabinet Office said nine out of 700 job centres had closed, while four courts had shut. Major airports including Heathrow said there had been no significant disruption or delays at immigration halls following stoppages by PCS members in the Border Agency.