The former leader of South Africa's main opposition party has sparked public outcry over a series of social media posts that suggested colonialism brought benefits to the country.

"For those claiming legacy of colonialism was ONLY negative, think of our independent judiciary, transport infrastructure, piped water," Helen Zille, the ex-head of the Democratic Alliance (DA) party and the current premier of the Western Cape province, wrote on Twitter on Thursday.

She also tweeted that the transition into "specialised health care and medication" may have not been possible without "colonial influence".

Zille's comments drew strong criticism from political opponents and those within her own party, as well as on social media.

Zille, 66, has since apologised, but she will face a disciplinary process by the DA, according to the party’s website.

Mmusi Maimane, who took the reins from Zille in 2015 to become the DA's first black leader, criticised his predecessor, tweeting "colonialism, like apartheid, was a system of oppression and subjugation. It can never be justified".

Maimane also told local media that Zille's tweets were "completely unacceptable and indefensible".

In a statement , the party reiterated Maimane’s remarks, saying colonialism "oppressed millions of people and violated human rights in a cruel and inhumane way".

The DA, which won 22 percent of the vote in 2014's general election, has been gaining popularity and trying to shed its image as a "white" party before 2019's presidential election.

It promotes itself as a liberal equal opportunity party, but efforts to broaden its appeal among black voters have been hurt by social media scandals, and the party has struggled to present itself as a credible alternative to the ruling African National Congress (ANC) Opponents demand Zille's removal

The ANC urged the DA to immediately remove Zille as Western Cape premier, calling her tweets "reckless and ignorant claims".

The Economic Freedom Fighters (EFF), another opposition party, also demanded  Zille "step down".

The EFF also called Zille's remarks "cold-hearted racism".

South Africa was colonised by the Dutch and British for about 300 years. The country then experienced white-minority rule under apartheid, which ended in 1994.

Racial tensions, however, have continued to endure in the years after apartheid.