James Franco has apologised after he unwittingly propositioned a 17-year-old fan on Instagram earlier this week.

Appearing on the Live! With Kelly and Michael show in New York this morning, the 35-year-old actor admitted that he felt awkward about the incident and had used "bad judgement".

Franco made contact with the Scottish fan, whose first name is Lucy, after she tagged a picture of him on her Instagram page while on a trip to New York City. She was said to have met the actor earlier outside the stage door of his Broadway show Of Mice and Men.

In a private exchange, he asked how long she would be staying in the city, commenting "You're single? ... Should I rent a room?" He then asked about her age, after she mentioned something about her 18th birthday present.

Lucy clarified she was "nearly 18" and eventually turned him down, saying "I'll come back when I'm 18".

She later posted about her decision to resist the actor, saying "james franco asked me to meet him alone! It was really him and I rejected him!! wtf am I doing".

Appearing on the talk show today, Franco told hosts Kelly Ripa and Michael Strahan he was "embarrassed" about the exchange.

"I was feeling awkward -- I didn't want to come on the show and just feel awkward," he said. "I'm embarrassed, and I guess I'm just a model of how social media is tricky. It's way that people meet each other today, but what I've learned -- I guess because I'm new to it -- is you don't know who's on the other end. You get a feel for them, you don't know who you're talking to. I used bad judgment and I learned my lesson."

"I used bad judgement" - James Franco apologises for underage Instagram chat