Broughton was ousted as Selwyn mayor by Lydia Gliddon in a landslide victory this month. Gliddon received 19,129 votes, beating Broughton (5277) by 13,852.
Broughton announced this morning he will step down as LGNZ president before the end of the year.
He was set to hold the role until the annual general meeting in June next year.
Broughton is currently attending the LGNZ mayors' school in Wellington.
"You’ll know that I wasn’t re-elected mayor," Broughton said in an email to LGNZ members on Monday morning.
"Over the past week, I’ve thought hard about what is best for LGNZ, and that’s why I’ve come to this decision."
Broughton was elected as LGNZ president in 2023.
He will now resign after the LGNZ national council meeting in early December.
The national council elections will be held over the next six weeks.
"Once the new national council is elected and has met I will transition out and hand over to that new board," he said.
Broughton served three terms as Selwyn mayor after being elected in 2016. He was also a Selwyn district councillor from 2010 to 2016.
He announced in January he would stand for a record-equalling fourth term, but his campaign remained largely low-key.
Broughton relied on his track record and argued he would provide stable leadership for a mostly new council.
Some viewed his LGNZ position as a distraction that left him out of touch with the district, though Broughton maintained it benefited Selwyn.
During his final term, the district council had two years of steep rate increases - 14.9% in 2024 and 14.2% this year.
Broughton said last week rates hikes were likely a factor in his defeat.
"We had larger-than-average rates increases in the last couple of years. You’d have to ask people individually why they voted the way they did, but I think that is part of the story here."
