Labour leader Phil Goff is unlikely to face any immediate threat to his leadership - but his position is shaky because of what one source described as a "bubbling" undercurrent for change.

There has been intense speculation about Mr Goff's hold on the leadership since news broke about a police complaint against MP Darren Hughes made by an 18-year-old male in early March.

Mr Hughes has denied any wrongdoing, but resigned on Friday, saying his position was untenable and he wanted to focus on clearing his name.

Speaking on Q+A yesterday, Mr Goff was adamant there was no threat to his leadership and he did not expect to face anger when his front bench meets in Dunedin tomorrow.

One Labour source said there was widespread discontent, but Mr Goff was safe because it lacked focus and there was as yet no clear runner to go against Mr Goff.

Although several names were in the mix, they lacked support or were unwilling to run against Mr Goff.

But there was another week before the next caucus meeting "and there's quite a lot of bubbling could happen in that period."

The crucial factor for Mr Goff's leadership would be the next round of polls. If Labour slipped below 30 per cent support, MPs would start to get nervous because many could lose their seats.

First-term MP David Shearer's name has been added to numerous suggestions about contenders, and one source said he had been approached as a potential challenger.

Mr Shearer firmly rejected the speculation yesterday, saying: "Seriously, where does this stuff come from?"

Other sources also discounted the likelihood of Mr Shearer being a willing contender or having the necessary support.

David Parker and the usual suspects Shane Jones and David Cunliffe, have all been suggested as starting to marshall support.

Last week Mr Jones and Mr Parker also repeatedly denied rumours any move was being made. Mr Cunliffe did not return calls yesterday or on Friday.

Some front bench MPs were yesterday downplaying speculation of a challenge or any serious confrontation with Mr Goff at tomorrow's meeting.

Maryan Street said the matter would almost certainly be discussed but she did not expect it to take up too much time.

Asked if she expected Mr Goff to be confronted, she said: "I'm looking forward to getting on with what we're meant to be doing."

Trevor Mallard said he had not spoken to anybody and did not know if there were widespread concerns.

Asked if he would raise any issues himself, he said: "I will raise issues myself if I think it's appropriate. But I won't tell you if I do."

The incident has also caused a rift between Mr Goff and party president Andrew Little who did not know Mr Hughes was being investigated until journalists told him. Yesterday he said he did not agree with Mr Goff's statement that it was a caucus issue and did not require Mr Little to be told.

"Any issue that bears seriously upon the party's reputation is not just a matter for caucus."

He was to talk to Mr Goff by phone last night.

Mr Little is in his last week as party president before he gives up the job to stand for Parliament.

On Q+A yesterday, Mr Goff said he kept it quiet as a matter of "justice over politics."

But the secrecy has raised questions about whether party leaders were hoping the issue would not become public until Mr Hughes' selection as Labour's candidate for Otaki in this year's election had been completed.

He was to have been confirmed by his electorate last Saturday.