NSW Premier Gladys Berejiklian has given one of her ministers a dressing down over an awkward love triangle involving members of the NSW Liberals' party room and the Prime Minister's staff, but she says that his job is not at risk over a "personal matter".

Ms Berejiklian is in the US at the National Governors' Association meeting, and was forced to answer questions about an alleged affair between NSW Innovation Minister Matt Kean, a close political ally, and party colleague Eleni Petinos, the member for Miranda.

Hornsby MP and Minister for Innovation Matt Kean pictured in a post uploaded to his Instagram page for Valentine's Day 2018. Credit:Instragam/Matt Kean

The incident was revealed on Thursday night when Mr Kean's ex-girlfriend, Caitlin Keage, a media adviser for Prime Minister Malcolm Turnbull, posted screen shots to social media app Instagram of an alleged text message exchange between the MPs after Christmas.

The screenshots were posted with the accompanying text: "When your boyfriend cheats on you when you're away with family @matt_keanmp."