Nuttall has faced trying times since he was elected party leader. He has had to deal with internal struggles within UKIP as well as the fallout from a failed bid for election in Stoke.
Farage, the former party leader, said on Radio 4 he would continue to support the leader of UKIP, but he had six weeks to prove himself.
The MEP made it clear the general election would be a major test of his leadership.
Farage revealed he is considering whether he would stand for election in the June vote, saying he had to "weigh it up".