Ms Main said a by-election must be held, under local government legislation, because a council seat cannot remain empty. A by-election is estimated to cost about $40,000.
She said Mr Laws had not formally advised her of his resignation - she had only heard media reports.
"While it will be disappointing to lose a councillor so early in the term, and the consequent need for a by-election, we recognise that people's lives change according to personal circumstances," she said.
Fellow Wanganui councillor Ray Stevens said by-elections had cost more than $100,000 in recent council terms and it would be more sensible to leave the seat empty or appoint the next highest polling candidate at the October elections - in this case, radio host Jason Granville.
In October he had suggested the council should lobby for a local government law change along those lines, but only councillor Jack Bullock had supported him. New district health board chairwoman Dot McKinnon had also not received a formal resignation from Mr Laws.
"I knew potentially he was leaving - I didn't know how things were going to pan out," she said.
He had been coming to all the main health board meetings meanwhile, but not committee meetings.
Ms McKinnon expected a letter of resignation from Mr Laws "at some stage".
A Health Ministry spokeswoman said health board by-elections were not permitted under law. Instead, the minister appointed people to fill seats left empty by elected board members.
Craighead is a boarding and day school for year 7-13 girls. It is a private school that receives state funding and has to fund its own building costs.
Mr Laws was reported as saying he was putting his children first in his role as solo father, and was looking forward to moving to South Canterbury.
