Darren Hughes has told his party he will formally resign before Tuesday, when Labour Party MPs will meet for their first full caucus since news broke about a police complaint against him by an 18-year-old student.

Mr Hughes announced last Friday that he would go but insisted he had done nothing wrong and would clear his name. Police are still investigating.

The office of Speaker Lockwood Smith yesterday confirmed he had not yet received a letter of resignation. A resignation is effective the moment the Speaker receives written notice of it, unless an MP states in the letter that it will take effect on a future date.

A Labour spokeswoman said Mr Hughes intended to have his letter with the Speaker before Tuesday, when MPs would return from a week-long recess.

At its caucus, Labour intended to elect someone to Mr Hughes' old post of senior whip, which could not happen until he had resigned. The role is currently being carried out by junior whip Steve Chadwick.

Labour leader Phil Goff has confirmed he will attend a meeting of the party's national council this weekend and expects to face questioning about his failure to tell president Andrew Little about the police complaint against Mr Hughes.

Mr Goff has previously said he withheld the news from Mr Little because he considered it a "caucus matter". However, the president has rejected that, saying anything that could damage the wider party is not solely a caucus issue.

Although the two have spoken since, Mr Little has refused to comment further.

He will step down as president at this weekend's meeting and Moira Coatsworth is likely to take over.

Labour's general secretary, Chris Flatt, said the national council would also discuss reopening selection for the Otaki seat. Mr Hughes had been intending to seek the nomination.

His decision to resign was bad timing for Josie Pagani, who lives in Otaki but was selected for the Rangitikei seat the day before he said he would be stepping down.

Mr Flatt said there were no plans to reopen the Rangitikei selection so Ms Pagani could seek Otaki instead.

Rangitikei is held by National's Simon Power, who is retiring.