The Congress of South African Trade Unions (Cosatu) said on Wednesday its leaders would lead marches around the country as part of a strike against corruption which workers say has led to job losses.

The strike, in which Cosatu is being joined by the country’s three other labour federations, coincides with the 13th annual Global Day for Decent Work and also seeks to highlight the plight of workers as a result of the Covid-19 pandemic.

In a series of posts on its Twitter account on Wednesday, Cosatu urged workers to stay away from their jobs and said some its members would gather in the capital Pretoria and march to the offices of the National Treasury. Similar marches would be held all around the country.

Cosatu has been in a tripartite alliance with the ruling African National Congress (ANC) and the South African Communist Party since 1990, helping the ANC stay in power since the end of white minority rule in 1994.

But it now says corruption has emerged among the biggest threat to the country’s hard-won democracy and is “like cancer eating at the moral fibre of our society and eroding the moral standing of our revolution and the cause for which our people laid down their lives”.

“Currently, we are in the midst of a massive corruption storm in South Africa, triggered by the Covid-19 demand for personal protective equipment ... and the general social service and relief necessities of the people and the country during this period,” it says in a list of grievances posted on its website to explain the nationwide strike.

“However, this does not mean corruption started with the Covid-19 procurement problems. It could only be a culmination of years of systemic corruption, abuse and deliberate weakening of public resource controls and the prioritisation of private interests over public goods and services in that regard.”

South African President Cyril Ramaphosa has ordered the Special Investigating Unit to probe allegations related to the misuse of funds related to the response to Covid-19, including the irregular awarding of procurement tenders.

His own spokesperson Khusela Diko is on special leave after being implicated in the graft, although she denies any wrongdoing.