Only the last four years of former president Jacob Zuma's administration became a problem for the African National Congress (ANC), party chairperson Gwede Mantashe said on Thursday.

He was speaking to News24 during his visit to Evaton on a campaign trail and said he disagreed with President Cyril Ramaphosa and finance minister Tito Mboweni that the Zuma years were wasted.

Mantashe accused Mboweni of being the originator of the slogan.

Ramaphosa has often spoken about the Zuma years as lost years and in November, while in East London, he called the past 10 years "damaging".

"We are trying to fix the damage that was caused in the past 10 years," Ramaphosa said.

But, while in Davos, Mboweni was reported to have called the Zuma years a waste.

Defending the "Zuma years", Mantashe said the National Executive Committee's opinions on the past nine years differed.

He said education, health and rural development had been stepped up by the last administration.

"It's a fact that education received more attention and access to education has increased dramatically. We built two universities, we are in the process of building another one. You can't say that was a waste. Access to ARVs (anti-retrovirals) was stepped up under the leadership of Jacob Zuma. It's not a waste, it reduced a number of deaths. Rural development received more attention."

Mantashe added: "You must come back and say the last four years became a problem, then you are describing the nine years. To just say they were wasted, you create an impression that nothing happened.

The "wasted years" is not a policy matter, but an analytical one, Mantashe said.

"There are no contractions, it's an analytical matter. It's not a policy matter. We can't stop thinking because the president makes a particular analysis and makes a particular conclusion. It's not empirical. This issue is a question of analysis and we must continue thinking," he said.

Free thinking, he said, was one of the ANC's strengths. "We can't give it away by toeing the line. It doesn't work that way."