Officials who embezzled, overpaid or failed to monitor spending ate up 20 percent of the government's procurement budget, Willie Hofmeyr, head of the Special Investigations Unit, told parliament, The Star newspaper reported Thursday.

Though difficult to pinpoint, a figure of 30 billion rand was "not unrealistic", Hofmeyr said Wednesday.

South Africa scored 54th out of 178 countries on corruption watchdog Transparency International's corruption perception index last year.

More than 40,000 public officials were found to have wrongly received social grants in an ongoing investigation from 2005, he said. The country will save 898 million rand in the future from the delisting of the grants, Hofmeyr said.

Public broadcaster the SABC is another big culprit, paying 2.4 billion rand to 20 employees' private companies from 2007 to early 2010.

Africa's largest economy needs to step up its anti-corruption police force from 700 to 7,000 to fight graft effectively, said Hofmeyr.

The unit secured 17,729 convictions out of 15,281 court cases, according to its annual report.