The letter asked for National's support and outlined details about the bill including its purpose, the reporting mechanisms and the proposed measurements for child poverty, as well as an offer of a briefing. It is understood a briefing before Parliament rose for the year would have been provided.
English replied a week later saying he wanted a briefing in the New Year, and stressing the importance of a strategy on how to lift people out of poverty. He made a plea for keeping National's Better Public Service targets as a tool for doing so.
Yesterday English criticised the Government for its lack of consultation over child poverty, saying it seemed more like symbolism rather than a genuine attempt for bipartisan support.
This morning Ardern said she was "saddened" to hear the criticisms and revealing that she had written to him 48 days ago.
Asked about the letter, English was adamant that it did not amount to a genuine bipartisan approach.
"We haven't had the opportunity to influence [the bill]."
Asked whether he had asked the Prime Minister's office for more detail and a chance to consult, he said: "We didn't do that. It was over the Christmas period.
"I don't think the Government ever intended us to be a position to influence that [child poverty] legislation.
"If you want genuine, multi-party commitment, you have to go through a genuine discussion about what the content is going to be. The Government has not done that."
He again criticised the Government for abolishing public service targets "just because it's the previous Government's initiative".
"That is not a sign of goodwill or bipartisanship. Maybe it was done to deliberately antagonise."
He said the previous Government had not consulted Labour on its approach to child poverty, but "we didn't pretend we were trying to be bipartisan".
English will have a briefing today before Ardern's announcement this afternoon.
Ardern said she still hoped to have cross-party support for her bill.
"Probably the thing that would be most political would be the targets themselves. That's why they're not contained in the law."