Member for the state's southwest, Louise Kingston, accused Shane Love of "relentless bullying and harassment" during an address to the state's Legislative Council on Thursday afternoon.
Mr Love says he doesn't know what he allegedly did to Ms Kingston and that he had tried to contact her but received no response.
"I think that this is the result of a difficult and bruising pre-selection process," he told ABC News on Friday.
"We have a small party but we're a party that actually cares about people."
During her address, Ms Kingston said she had raised the issue with Mr Love and others but did not make a formal complaint because she believed the situation had been resolved.
She also told the chamber she had been "punished by an underhanded campaign" during preselection earlier in June, "and the party decided I was not worthy to be a part of their team going forward by preselecting me in an unwinnable position".
Nationals WA president Julie Freeman previously said the party had a robust harassment complaints policy and the state director had confirmed that no complaints had been lodged regarding the issue raised by Ms Kingston.
Ms Kingston took over the southwest seat in September 2023 after Nationals-turned-independent James Hayward was booted from WA's parliament.
Hayward resigned from the WA Nationals after being charged in 2021 with child sexual abuse but continued to sit in the state's upper house as an independent MP.
Hayward is serving a prison term of two years and nine months after being convicted in October 2023.
In November 2023, more turbulence hit the party with Nationals MP Merome Beard swapping camps to join the Liberals.
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