Lianne Dalziel's looming resignation to contest the Christchurch mayoralty has sparked speculation Labour will stand list MP Clayton Cosgrove in the byelection for the seat, opening the way for Northlander Kelvin Davis to return to Parliament.
Ms Dalziel confirmed she would stand against Mayor Bob Parker in the local body elections in October and would resign as an MP before then.
She said she was likely to time her resignation so a byelection would not clash with the local body elections - something she said would be unfair to candidates in both.
That means a mid to late November byelection is likely.
Ms Dalziel would not say whether a new person or a current MP should replace her but expected the electorate to attract a large number of candidates. Some in Labour believed Mr Cosgrove, who lost the Waimakariri seat to National's Kate Wilkinson in 2012, should stand in Christchurch East instead. Other possibilities mentioned within Labour include Problem Gambling Foundation adviser Tony Milne and former Labour MP David Caygill's son, James Caygill. Mr Caygill is a consultant to Ngai Tahu and has worked as an adviser to Helen Clark.