nzherald.co.nz will have full coverage of today's Budget, with news, comment and analysis from 2pm.

Maori Party MP Hone Harawira sought permission to cross the floor to vote against today's Budget because of his objections to any increase in GST - a move that would have breached his party's agreement with National.

Mr Harawira said yesterday that he had asked but was refused because the agreement required all five Maori Party MPs to vote for the Government on confidence and supply matters.

He said he had agreed to abide by that, but had repeatedly raised his concern about the party supporting the GST increase both verbally and in writing, believing it would hurt most the people the Maori Party represents. It is also against Maori Party policy.

"I'm having difficulty supporting a tax increase that made things easier for the wealthy at the expense of those in need.

"Maori people ... voted for us because they believed in us and they will be struggling to put the picture of the Maori Party they voted for together with the picture of their MPs voting for an increase in GST."

Although the passing of the Budget does not depend on Mr Harawira's vote, it would have further strained the relationship between National and the Maori Party.

Mr Harawira agreed to abide by the agreement after his colleagues urged him to do so to help secure the party's own policy wins such as Whanau Ora, the Foreshore and Seabed Act repeal and the tobacco inquiry.

"Those are things that would never have happened under National alone or under Labour alone so I understand completely where my colleagues are coming from."

He said his party had fought against the GST increase behind closed doors and that it was all "National's decision".

However, his party owed it to their constituents to at least speak out against it.

The Maori Party MPs have used their "agree to disagree" clause frequently - but never on a confidence and supply matter.