The president said: "We must acknowledge that our movement, the African National Congress (ANC), has been and remains deeply implicated in South Africa's corruption problem."
He added that though there are others involved in the problem the ANC "does stand as accused number one".
One issue he highlighted was local ANC leaders using "food parcels meant for the poor to buy political favours from those people in the branch or broader community".
He said that the government was now taking action but the fight against corruption required a commitment from all members.
The problem both robbed people of money that was due to them but also rendered some parts of the country's infrastructure dysfunctional.
Ramaphosa replaced then-President Jacob Zuma as leader of the ANC in December 2017 on a pledge to tackle the corruption that dogged Mr Zuma's government.