"These do impact, but we'd like to make sure that it's put in perspective,'' he told Radio New Zealand.
Mr Bush said they were only three cases, compared with the 130,000 prosecutions last year.
"The New Zealand police is absolutely focused on the trust and confidence that the New Zealand public has in it ... It's really pleasing that at the moment, the trust and confidence that the public have in us is at 77 per cent. That's the highest I think it's ever been.
"But that's not good enough for us. We want to maintain and grow that trust and confidence, because it makes us do a better job.''
Mr Bush said police did not take part in undercover operations without "a really considered and measured approach'' and legal advice.
"The law is open to a number of interpretations. We try very hard to get it right. We take the best advice we possibly can. But as we know with our system, every legal decision is reviewable as it goes up the line.''
Asked if it was standard practice to clear operations with a judge, Mr Bush said: "If we were to do anything like this, we would seek the direction or the permission of the judiciary. And as you've heard in this case, we did absolutely that.''
The operation against the gang was overseen by the Organised and Financial Crime Agency of New Zealand (Ofcanz) and headed by Detective Inspector Grant Wormald, who also headed the joint raid on internet millionaire Kim Dotcom's mansion for the agency.
President of the Criminal Bar Association and former undercover policeman Tony Bouchier said the agency's involvement in the two high-profile cases raised questions about its methods.
"Certainly if you look at the Dotcom case and you now look at this particular case you might be forgiven for thinking they're more result-driven than they are concerned about the way in which they achieve those results.''
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While the agency's involvement in the Dotcom case could be seen as "a series of blunders'', the Red Devils case was more serious.
"It's different in nature, it's about maintaining the integrity of our independent judiciary and the criminal justice system in New Zealand.''
Mr Bouchier called for an inquiry into Ofcanz by the Independent Police Complaints Authority or a Queen's Counsel.
Police Minister Anne Tolley yesterday defended Ofcanz and its methods.
"I have no doubts that Ofcanz are doing their very best to fulfil their function, which is to make sure that we do not have organised crime continuing to operate in our country.
"We cannot tie both hands behind their backs and expect them to be able to break into and break up these very sophisticated criminal organisations.''
