Nationals Senator Bridget McKenzie says Craig Kelly’s resignation from the Liberal Party means the “door’s always open” for him to join the Nationals.

Outspoken backbencher Craig Kelly told the Liberal party room on Tuesday he is quitting the party and will remain in parliament as an independent, but has ensured the government he will continue to provide supply and confidence.

Mr Kelly told Sky News his decision to resign from the Liberal Party is with a “very heavy heart” but maintains the move is necessary if he’s to speak up on his beliefs and best represent his constituents.

Ms McKenzie told Sky News the former Liberal MP has “joined with our party” on a number of policy issues in the past including on energy and support for small businesses.

“There is a lot of synergies with Craig’s view of the world and what we come to Canberra to fight for,” she said.

“The door’s always open but that at the end of the day is a matter for Craig.

“We’re always looking for ways to grow the National Party.”