NSW MP and former treasurer Matt Kean resigns from parliament

Former NSW Treasurer Matt Kean has announced his resignation from state parliament, ending his 13 years as the member for Hornsby.

Mr Kean dashed rumours he was making a tilt for federal politics, saying he would be pursuing opportunities in the private sector.

The Liberal MP made the announcement with his wife Wendy and four-year-old son Tom in a snap press conference on Tuesday afternoon, just hours after Labor Treasurer Daniel Mookhey handed down his second NSW state budget.

Despite his own big news, he did not miss the opportunity to take a dig at the government's efforts.

"Thank you for coming out and I'm sorry to take you away from the worst NSW budget in modern history, but I've got another announcement to make," he began.

"Today, after 13 years as the member for Hornsby, I'll be retiring from parliament."

NSW MP and former treasurer Matt Kean

Mr Kean said he had made the decision over the weekend and denied he timed the announcement to detract from the budget.

"I've been thinking about this for some time and over the weekend, I made up my mind," he said.

"This is the last sitting week before the winter break and I don't intend on coming back to the parliament in the August sittings."

His announcement was attended by several Liberal MPs, including Opposition Leader Mark Speakman, Felicity Wilson, Eleni Petinos and NSW Liberal state director Richard Shields.

While he said hadn't confirmed a new role, he said he intended to pursue a role in the "energy and climate-related space".

"I'm passionate about energy, and I'm passionate about the transition (to renewable energy). This transition is inevitable," he said.

"I've made an impact when it comes to public policy and I want to make an impact ensuring that not only energy users benefit from this transition but our economy benefits and our environment benefits."

Former NSW treasurer Matt Kean made the announcement alongside his wife, Wendy and their four-year-old son, Tom. Picture: Supplied

Under the former Perrottet government, Mr Kean served as the energy minister, treasurer, and was the deputy NSW Liberal Party leader until the Liberals lost the state election in March last year.

His resignation will trigger a by-election in the northwestern Sydney seat.

While Hornsby has been held by the Liberal Party since its creation in 1950, Labor won an 8.8 per cent swing against Mr Kean in the last election.

His resignation comes amid growing speculation about the departure of former premier Dominic Perrottet, who holds the nearby seat of Epping.

However when asked, Mr Kean declined to offer his pick for his successor, saying it was "a matter for the Liberal Party.

"A by-election isn't a new thing in public life. This won't be the first by-election, and it certainly won't be the last by-election, that's the NSW political process," he said.