John Legend's model fiancee Chrissy Teigen has fired back at unsubstantiated rumours suggesting the R&B star cheated on her with another woman during a recent night out in New York.

Reporters at the New York Post published a gossip article on Thursday (09May13), accusing the Green Light hitmaker of enjoying a steamy smooch with a mystery blonde while partying at Manhattan hotspot Acme last Friday (03May13).

Sources claimed Legend pulled the lady into a bathroom for a "steamy make-out session", but the allegations have infuriated Teigen and she has blasted the rumours and publication bosses in a series of angry posts.

She writes, "Just read John cheated on me and in the uber-credible Post. I'm just heartbroken as it's definitely not typical post bulls**t.

"The @nypost is normally so kind to me. And I am normally not the one to use the term s**t rag so I guess we're both a little off today."

Legend and Teigen became engaged in December, 2011. They have yet to set a wedding date.