President Jacob Zuma on Sunday, lambasted the ANC Youth League, saying its members conducted themselves as if they were a lost generation and their behaviour was not acceptable.

His comments followed a boycott of the provincial conference of the ANC by the Free State youth league at the weekend. The league claimed the conference was illegitimate.

Zuma said there were vast differences between the league of today and the league as it was in its heyday. The league previously raised issues in a comradely way and did not organise meetings or insult party leaders.

"Only those who don't have the ANC in their blood will do so [boycott an ANC conference] . only those who don't understand and believe in the ANC," Zuma told delegates in his closing remarks at the ANC Free State conference.

Zuma said that, like the youth of the 1950s, the league of today needed to know what its role was, and that its current leaders could not create new roles for it.

"They [the youth of the 1950s] never attempted to shape the ANC outside there ... in slogans and in meetings that you cannot describe," he said.

Zuma was referring to a rally on Saturday organised by the "young lions" in Bethlehem.

The league boycotted the ANC elective conference in Parys, the home town of the party's provincial chairman, Ace Magashule, claiming it was illegitimate.

Zuma offered condolences to the families of those who died in a bus crash returning from "this gathering of some sort".

He said "those comrades would have come back and the chair [Magashule] would have engaged and persuaded them, showed them how the ANC leads and lives".

"I'm not certain whether the youth of today is anything that inspires. I'm not certain the things some of our youth are doing inspire at all."

Zuma said each generation of the young carved out its own niche, adding that the youth of today had a critical duty to defend the democratic gains of the freedom struggle.

In an indirect attack on expelled youth league president Julius Malema, Zuma said: "The ANC must discipline everyone equally. Those who think they can bend around the constitution for their own selfish ends must be dealt with."

Malema was expelled for fomenting division in the party.

Zuma gave the Free State conference his blessing, saying it has been convened constitutionally. He criticised those who differed, saying they had conducted themselves in an "un-ANC" way.

He said the provincial ANC leadership had been meticulous in dealing with complaints by individuals and branches, to the extent of postponing the conference three times.

Zuma has the backing of Magashule in his bid to be re-elected ANC president in Mangaung.