Owen Smith has found himself in a spot of trouble over the language he used in a speech to party members in Hammersmith last night.
"What you won't get from me is some lunatic at the top of the Labour Party" he said, sparking outrage from many.
Corbyn's camp weren't particularly pleased by the comment either.
This morning Smith admitted he needs to be "slightly less colourful" with his choice of language. He told the BBC Radio 4 Today programme that he was not referring to his Labour leadership rival, Jeremy Corbyn.
He said: "Having been accused earlier in the evening of running around like a lunatic, I was saying I wasn't a lunatic, but if anybody's offended by the use of that word then I do apologise and I've done that already this morning and I'll do it again.
"But I wasn't talking about Jeremy. I was talking about me."
This is by no means the first time Smith has faced criticism for what many see as un-PC comments. He has previously apologised for claiming that Labour should "smash" Prime Minister Theresa May "back on her heels".
Smith was asked on the Today programme whether his comments showed he was not ready to be Labour leader.
"I don't think so," he said.
"I think it suggests that I'm occasionally a bit colourful with my language. I need to be slightly less colourful perhaps in future."