The “straw that broke the camels back” in the Barnaby Joyce saga turns out to be a former West Australian Rural Woman of the Year who made a sexual harassment complaint about Mr Joyce.

After weeks of turmoil after the former Deputy Prime Minister’s relationship with a former staffer, an animal nutritionist and jillaroo from Kununurra, Catherine Marriott, said in a statement she wanted to speak up against inappropriate behaviour.

In a statement, Ms Marriott said she never intended for the issue to become public and had asked for the National Party to undertake a “formal and confidential” investigation into the incident.

“I requested that … to ensure there is accountability in relation to the incident I raise, and to prevent this type of inappropriate behaviour towards women in the future,” Ms Marriott said.

This complaint was not made solely to address the incident against me — it is about speaking up against inappropriate behaviour by people in powerful positions.

“I will await the outcome of this investigation before determining any future action or commenting further.”

Mr Joyce has called her allegation “spurious and defamatory” — and has called for the matter to be referred to the police.

He said his decision to step down was confirmed when he read about the allegations in the newspaper on Friday.

“I just thought that has to be the straw that breaks the camel’s back,” Mr Joyce told media when announcing his resignation as the leader of The Nationals and as the Deputy Prime Minister.

Ms Marriott is an elected councilor at the Shire of Broome in Western Australia, a former chief executive of the Kimberley/Pilbara Cattleman’s Association and project manager of the Cooperative Research Centre for Developing Northern Australia.

A former West Australian Rural Woman of the Year, Ms Marriott is a passionate advocate of Australian agriculture and the role of women in rural communities.

In 2013 Ms Marriott addressed the Rural Women of the Year awards and said women needed to effect change in their communities.

“Be the change you want to see in the world,” she said. “It is far easier to sit back and say somebody needs todo this, somebody should do this. Well guess what I am somebody and you are somebody and together we can create change.

Ms Marriott’s lawyer, Emma Salerno, said her client was determined to see the Nationals follow her complaint through to its conclusion, The Australian reported.

“What was most difficult and what prevents a lot of people in circumstance like this [from coming forward] is the repercussion of being dragged through a scandal,” Ms Salerno told the newspaper.

It comes as Prime Minister Malcolm Turnbull endorses Mr Joyce’s decision to resign from Washington DC before meeting United States president, Donald Trump.

“This is really a very personal matter for Barnaby. He has to deal, as he said, with some personal issues, he’s got to deal with a complaint that’s been made about him as he said he believes he cannot do that from the dispatch box,” Mr Turnbull said.

“I look forward now obviously to working with the new leader of the National Party who will be elected on Monday,

“Barnaby made his own decision to take leave to reflect on the circumstances and deal with personal matters.”

The Nationals party room meets at 8am on Monday, with the contest likely coming down to two candidates, ministers Michael McCormack and David Gillespie.

Six hours later, the new leader will face his first question time test, with Labor expected to zero in on the secrecy behind the coalition agreement – a private letter exchanged between the Nationals and Liberals leaders which forms the basis of how they work together.

-With ABC/AAP