Decisions by former deputy premier Andrew Stoner while a minister should be the subject of an independent review following revelations he was the victim of a blackmail attempt, Labor says.

It was revealed on Monday that Mr Stoner was targeted by blackmailers who had made contact with him via the professional networking site LinkedIn.

Mr Stoner reported the matter to police in November, shortly after he suddenly quit as Nationals leader and then left cabinet in mid-October. He retired from politics at this year's election in March.

He has said police have advised him not to comment but denies there were "images" involved.

Police sources have confirmed that blackmailers – including from west Africa – are targeting politicians via LinkedIn by luring them into compromising positions before demanding payment.

Premier Mike Baird has said it is "a personal matter" for Mr Stoner and "there's nothing to suggest that was has taken place has in any way impacted his ministerial responsibilities."

But the exact timing of the blackmail attempt remains unclear, leaving open the possibility it occurred while Mr Stoner was deputy premier and the minister for trade and investment.

Opposition Leader Luke Foley said the revelations meant "there is now a very serious question mark" over decisions made by Mr Stoner in office."As the second most senior politician in the state, Mr Stoner had disproportionate influence and sway over key decisions made by the government – including periods when he served as acting premier," he said."Mike Baird should appoint an independent reviewer to assure the community that the commercial decisions made by Mr Stoner during this period were free from undue influence."

But a spokesman for Mr Baird said: "This is a personal matter and the Premier does not have any information to suggest otherwise.

"He'll leave the matter to police and Mr Stoner."