"During his time with Magic Talk, Sean has engaged his audience with many vibrant discussions and I wish him all the best for his future endeavours."
An update on who would host the afternoon show on Magic Talk would be made in "due course", Wallace said.
The news came after the veteran broadcaster was missing from his show yesterday for the second day running, with Stephen McIvor filling in for him.
The afternoon talk-show host has been off air this week after stand-in host John Banks last month endorsed the views of a caller who described Māori as "stone-age people with a stone-age culture".
The racist dialogue caused an uproar. At least one major corporate suspended advertising with the station and New Zealand Cricket, which had only just signed a three-year broadcasting partnership deal, threatened to review its relationship with Magic Talk.
Banks was replaced and Wallace announced the fill-in broadcaster would never get another job at the station while he was at the helm.
But as colleagues distanced themselves from the former Auckland mayor, Plunket posted a tweet appearing to sympathise with the outspoken broadcaster.
The radio personality was asked not to return to Magic Talk and management was reported to be in crisis talks.
Today, Plunket did not want to talk about his departure or the Banks incident.
Plunket's show Magic Afternoons with Sean Plunket ran weekdays from midday-4pm.
It had courted controversy in the past year, earning a stiff rebuke and a fine from the Broadcasting Standards Authority over allegations of racism.
In December, the BSA rebuked MediaWorks after a May 6 Plunket interview with Te Whānau ā Apanui spokesman Louis Rapihana on Covid-19 checkpoints.
The BSA said the interview amplified negative stereotypes about Māori and had the potential to cause widespread harm.