He has spent nine years as an MP.
Muller spent 53 days as National Party leader, having spearheaded a coup against former leader and Tauranga MP Simon Bridges.
Muller’s breakdown forced him out of the role, throwing the party into turmoil just months before the general election. He was later demoted under Collins’ leadership from party rank eight to 19.
“In all jobs there comes a time when, if you are honest, you start lacking the enthusiasm and energy you once had,” Muller said.
Muller had previously planned to quit politics in 2021 after admitting he had been an anonymous source in an article criticising returning MP Harete Hipango.
However, he later changed his mind.
National leader Chris Luxon said Muller had been a “deep-thinking and hard-working” National MP.
“Politics requires an enormous commitment to do the job well and I respect Todd’s decision to call time and retire from Parliament at the upcoming election,” Luxon said today.
”Every politician needs a team behind them and I thank Todd’s family, current and former staff, and party members in his electorate for their support of him.”
Todd McLay would take over Muller’s agriculture portfolio.