Tabloid reports had previously hinted at a romance between the pair after they partied together following the ceremony on Wednesday night.
An apparent “on-looker” told The Sun they were getting close, with James “kissing her cheeks and forehead”.
However, James has now responded to the story on Twitter, calling it a “sad state of affairs”.
He wrote: “Firstly, we were not kissing we were talking closely because it was loud as fuck in a club. Have you ever tried having a conversation when theres loud music? You gotta be tactile.
“Sad state of affairs when a guy and a girl can’t sit and chat without being romantically involved.”
James then slammed the person who had covertly pictured them at the bash, adding: “What kind of a person sneaks pics of people sitting and chatting at a party. Scruffy that.”
Earlier in the evening, Jesy arrived on the Brit Awards red carpet with a friend, after all of her other bandmates brought along their boyfriends.
The kiss was even referenced by Brits host Jack Whitehall during a chat with Little Mix, as he joked: “You girls have a wonderful time at the after party, night clubs, kebab shops or wherever you naughty Little Mixes get up to mischief.”
Jesy split from split from her ex-boyfriend Harry James in November after 16 months together. Prior to that, she dated TOWIE star Chris Clark.