A case of assault has been opened against African National Congress Youth League (ANCYL) leader Julius Malema, Gauteng police said on Tuesday.

"A case of assault was laid at the Bramley police station during the day yesterday [Monday]," said Superintendent Eugene Opperman.

"It will be investigated and forwarded to the senior state prosecutor for a decision."

The Star newspaper reported on Monday that a neighbour of Malema was assaulted during a party at the youth league leader's house in Sandton, Johannesburg.

The newspaper said that the neighbour, who is a police reservist, had laid a charge at the Sandton police station.

But ANCYL spokesperson Floyd Shivambu said when he checked on Monday morning, no charge had been laid at the Sandton police station.

Opperman said the charge was only laid on Monday during the day.

Malema said on Monday the latest allegations were all part of a conspiracy to undermine the leadership of the youth league.

"They are sent by Helen Zille [DA leader] and her people to come and spy on us."

He criticised The Star for publishing a story with an unnamed source.

The police reservist's name has not been made public.

"We don't entertain faceless accusations," said Malema.