Julie Anne Genter secret letter saga lands in the House for fourth day

Julie Anne Genter has revealed in Parliament that she signed her secret letter as the Associate Transport Minister, after insisting she didn't write it in that capacity.

She's refusing to release the letter she sent to Transport Minister Phil Twyford over Let's Get Wellington Moving in March this year.

Today in Question Time Genter said she signed the letter as the Associate Transport Minister.

This is after Genter yesterday said she wrote the letter in her capacity as a Transport spokesperson for the Green Party.

She avoided questions from media asking her to clarify what capacity she wrote the letter in.

"The decision that we've made about releasing the letter is about the content of the letter, which was conveying the Green Party's political views and it is standard practice not to release that political consultation but I'm quite happy to discuss in my Associate Transport Minister role anything to do with Let's Get Wellington Moving."

National's Transport spokesman Chris Bishop said which capacity Genter sent the letter in was important.

"The fact that she's trying to say she sent it as a Green Party MP is essentially a cover to make sure she doesn't have to release the letter and won't be forced to."

Twyford said he understood Genter sent the letter in both her ministerial capacity and as a Green Party spokesperson.

"She was writing as the associate minister but expressing a view on behalf of the Green Party so it's not all that easy to separate those things out."

The letter's fuelled speculation about the part Genter played in putting a second Mt Victoria Tunnel on the back burner in the $6.4b transport project.

Bishop said he believed the letter had put the tunnel on the "never never".

"The truth will out in the end and Wellingtonians will find out just what influence the Green Party's had on Labour Party transport policy", he said.

Genter has put some rumours to bed saying she never threatened to resign over LGWM, and the confidence and supply agreement between the Greens and Labour was never put in jeopardy.

The Chief Ombudsman is investigating her refusal to release the letter.