NSW Premier Gladys Berejiklian has called on Labor to rip up its preference swap with the Shooters, Fishers and Farmers Party days out from the state election, as Opposition Leader Michael Daley sought to downplay his deals with the minor party.

A day after John Howard appeared in anti-gun advertisements for the Liberals, the former prime minister joined Ms Berejiklian on the campaign trial in the western Sydney seat of Penrith.

NSW Premier Gladys Berejiklian is joined by former prime minister John Howard as they take to streets in Penrith on Monday. Credit:Nick Moir

Mr Howard on Monday defended his appearance in the ads, in which he says the Shooters party had wanted his signature 1996 gun laws repealed and would put "enormous pressure" on Labor to do so if it were to win.

He said the ads had been filmed before the Christchurch terrorist attack and expressed his condolences.