Embattled Women's Minister Louise Upston declined the opportunity to speak at the National Council of Women's 120th Anniversary Conference, telling them she was too busy.

Council president, Rae Duff, told Newshub the invitation was made to Ms Upston, but turned down with the minister saying she did not have time.

But an email trail released to Newshub by the minister's office late this evening shows she was only asked to accompany the Prime Minister to the opening or speak on his behalf if he couldn't make it.

"She didn't have the time to speak unfortunately," Ms Duff said.

Ms Upston has been criticised for not speaking out during the Chiefs' stripper saga.

However, Prime Minister John Key did have time to speak and opened the conference - with Ms Upston sitting in the audience.

Mr Key told Newshub he expected Ms Upston to speak if she was asked.

"Well if they invite her to, yes it would be great."

Mr Key recognised the significance of the organisation, which was founded by suffragette Kate Sheppard.

"They've got a great story to tell I mean, Kate Sheppard was their founding leader you know 120 years ago," he said.

"It's a remarkable contribution that she made and New Zealanders are rightfully proud of the fact that we were the first country in the world to give women the vote but as has been pointed out while a lot of progress has been made, the job is not complete there's more to be done."

Other guest speakers at the conference include Ministry for Women chief executive, Dr Jo Cribb, Equal Employment Opportunities commissioner Dr Jackie Blue and Auditor-General Lyn Provost.

Newshub tried to ask Ms Upston why she declined the invitation to speak, but she refused an interview saying she had to rush off to a select committee.

Newshub.