The NSW Liberal Party has suspended upper house MP Peter Poulos after revelations he leaked explicit photos of a female colleague five years ago. 

It came a day after Mr Poulos tendered his resignation as parliamentary secretary over the issue, and just weeks before voters go to the polls on March 25.

"This afternoon, the State Director, in consultation with the State President, exercised campaign powers to suspend Peter Poulos from the NSW Division for a period of 6 months," a spokesperson for the Liberal Party said in a statement.

In his apology to Robyn Preston, the woman in the pictures, who was running for preselection for the seat of Hawkesbury at the time of the incident, Mr Poulos called his action a "regrettable mistake".

Ms Preston this week told reporters she had accepted his apology and considered him a friend.

It now means the moderate-faction MP has been disendorsed as a Liberal candidate and will be removed from the upper house ticket for next month's election.

On Wednesday, Premier Dominic Perrottet stood by Mr Poulos's candidacy, saying people made mistakes and Mr Poulos apologised for his.

By earlier Saturday, the premier had distanced himself from the embattled MP, calling on the party to act.

"When that situation occurred years ago I was appalled, horrified, and disgusted. I was very close with Robyn Preston … I know the distress at that time that that caused her," he said.

"There is no place for that behaviour in any workplace, I have made that very clear. I expect the New South Wales Liberal Party to act appropriately as well." 

The party will now look to urgently look to fill his vacancy on the ticket.

In 2021, Mr Poulos was appointed the parliamentary secretary for Wollongong and the Illawarra.

Prior to that, from 2004 to 2016 he was a councillor for Rockdale City Council where he served as deputy mayor for one term.

He has been a member of the NSW Liberal Party since 1993.