The ANC on Tuesday slammed DA MP Mike Waters for posting a "racist" tweet and labelled the DA as a collection of racists.

"We are neither shocked nor surprised by this behaviour from a member of the DA as the party proves on a regular basis that it is nothing but a collection of bigoted racists who continue to regard black people as sub-human... dogs," said spokesman Zizi Kodwa in a statement.

On Monday, Waters posted a picture on social network Twitter showing a pack of dogs lining up towards a tree, underneath which was a picture of President Jacob Zuma.

Kodwa said Waters likened people who voted for the ANC to dogs.

"They [DA] have failed to convince the electorate of their policies. They have nothing to offer except to continuously insult the intelligence of people of this country and attack their leadership," Kodwa said.

Waters has since deleted the tweet and apologised on the social network.

Democratic Alliance spokeswoman Phumzile van Damme said the party had accepted Waters' apology.

"Mike has unreservedly apologised for the tweet. He is not a racist person and has acknowledged that the picture is offensive and distasteful, and we have accepted that," Van Damme said.

She said the party would soon review its social media policy.