"There was some doubt about the numbers and given that, I thought it was a good idea to separate it from the substantive piece of legislation."
United Future Leader Peter Dunne yesterday confirmed the spending cap was removed as a result of his opposition.
"There was a serious constitutional principle here of one Parliament effectively binding its successor.
"That's never been part of our constitutional arrangement and I also think that it's an impractical idea anyway."
Mr Banks said he respected Mr Dunne's point of view but the United Future leader had indicated he would support the standalone legislation for the spending cap at its first reading.
Mr Dunne said he "may well" support the legislation to the select committee stage, "but I've made it very clear to Mr Banks right the way through that my objections are paramount and I would not support it beyond that stage."
A spokeswoman for Mr English said the spending cap legislation would be a Government bill under Mr Banks' name and National would support it at all stages.