The WA Premier says he has been "assured" the sacking of a media advisor who was working for Health Minister Roger Cook was unrelated to allegations she made about bullying and harassment.

Mr Cook's chief-of-staff Erik Locke resigned on Friday after it emerged he sent an inappropriate email and text message to media advisor Jane Grljusich late last year.

It is alleged Mr Locke referred to Ms Grljusich in the email as "Kim Jong Lard" and suggested in the text message how she could pay for a liposuction procedure.

A State Government spokesman said on Saturday that Mr Locke resigned for "personal reasons".

Erik Locke sent Ms Grljusich an email allegedly referring to her as 'Kim Jong Lard'. ( Linkedn: Erik Locke )

But Premier Mark McGowan confirmed Mr Locke offered his resignation after media questions about the email and text on Friday.

"Obviously there was a personality conflict," Mr McGowan said.

"I'm not very happy with what has taken place and he has now offered his resignation and it's been accepted.

"I don't want to get into the business of character assassination and so I really don't want to, and I won't, make comments about the individuals involved."

Ms Grljusich, the daughter of the late broadcaster and footballer George Grljusich, engaged a lawyer after being sacked last year.

Mr McGowan said he had been assured Ms Grljusich's contract was not terminated as payback for her making a bullying complaint against Mr Locke.

Mark McGowan says there was a "personality conflict" between the pair. ( ABC News: Rebecca Carmody )

"My understanding is that there were other issues, other unrelated issues that resulted in that outcome," he said

But Mr McGowan could not explain why Department of Premier and Cabinet director-general Darren Foster had commissioned an independent inquiry into Ms Grljusich's claims instead of referring the matter to the Public Sector Commission.

"I don't know the answer to that," he said.

"The Department of Premier and Cabinet has handled this issue. It wasn't something I made decisions about."

Mr McGowan's office said Mr Locke was not eligible for a payout because he left of his own accord.

Ms Grljusich said her lawyer wrote to Mr McGowan last November, after her termination, to outline the nature of her complaint.

"The director of communications Daniel Pastorelli was informed of the issues on the 3rd of November after Erik Locke asked him to move me," she said.

"I was told Darren Foster would make enquiries with me. He did not.

"I followed up several times about this before I was terminated on November 8.

"A letter outlining some of the horrific treatment I endured was sent the Premier on 20 November."