Burnham was asked about his view on the risk of opening up the mayoralty to a Reform challenge had the NEC decision gone the other way.
“My analysis on that is the party would be better to get on the front foot now in terms of the challenge that’s out there,” he said.
He described the current state of politics as “very serious” and suggested the country was at a “fork in the road”, similar to Brexit.
“I took the judgement to start on the front foot and win now, I think [Reform] can be beaten now because I think they have made a mistake in bringing the worst of the Tory party in to Reform,” he said.
“What I was offering the party, I think, was an alternative path to the one that the party is now on.”
Asked about why Westminster has a perception of being a “working class free zone”, Burnham said: “That question goes to the heart of everything for me.”
He suggested it was more difficult for working class representatives to make it than in the past, when there was a “stronger route” from Trade Unions.
“You kind of get the feeling the way you get spoken about is different, there’s a club down there you feel that you’re never really a part of,” he said.
On Tuesday, Reform announced it had selected GB News presenter and academic turned activist Matt Goodwin as their candidate for Gorton and Denton.
Other parties are yet to announce their candidates for the contest.