Keith Barwell, the Chairman of the English club, told the BBC that Van Niekerk had signed with the club, but that his contract contained a clause that allowed him to abandon the decision if the club failed to avoid relegation.
But Cathy van Niekerk said that this was not the case.
“At the moment Joe is signed with Western Province, the Stormers and the Springboks.
“There are many offers on the table, and Joe will make a final decision at the end of the week.”
She did not deny however that it was a strong possibility that Joe might sign with Northampton.
“They may be down at the moment, but they will come back,” she said, speaking of their possible relegation this weekend.
“But this is the very reason they look to sign players like Joe, to revitalise their sides.”
The player’s agent said she would phone Barwell to clear up the misunderstanding.
She did also confirm that Van Niekerk would remain in South African rugby until at least November 1, in a bid to win his fiftieth cap – he is four shy – and to play in the World Cup for the Boks.