Jackson said Seymour's perspective was "no different from Brash's".
"He perpetuates lies and myths, he tries to make out Article Three rights don't exist, he tries to make out every single person has the same right - the reality is he's trying to deny Māori have a Treaty right. That Treaty right is not a superior right, it's an equity right - it brings Pākehā and Māori people together."
Jackson said it was "sad" to see Seymour's Māori policy considering he had "claimed he was Māori" previously.
Seymour does not just "claim" Māori heritage, he is Māori and has links to the Ngāpuhi iwi on his mother's side.
Jackson clarified the "claimed" part of those remarks, and said he accepted Seymour's claim to Māori heritage.
"He has claimed his whakapapa - I was there at the hui in 2017.
"He's just a useless Māori, that's all. You can't deny any people their whakapapa, it doesn't make them some great advocate for Māori, does it?"
Jackson said Seymour was the "worst advocate for Māori in terms of politics - I have never seen anyone like it".
"[He's] absolutely Māori, but just maybe the most useless advocate for Māori we've seen in Parliament".
In response, Seymour said Jackson had not been able to defend his own ministry.
"The fact Willie chose to personally attack me instead of explaining what value Te Puni Kōkiri adds just shows why we should get rid of it and save the taxpayer $71 million.
"I feel sorry for TPK staff, even the responsible minister can't explain what value they add, less kind people would say that's a useless minister."
Jackson called on National to be clear about where it stood in relation to Act's alternative budget.
National leader Christopher Luxon would not rule out individual parts of the budget but said abolishing ministries was not his party's policy.
