EXCLUSIVE

Josh Murray and Amanda Stanton split after he ditched her at a concert ... and it was the straw that broke the camel's back, TMZ has learned.

The incident went down earlier this month when the "Bachelor in Paradise" stars attended Jingle Ball at Staples Center with a few 'BiP' co-stars.

Sources close to Amanda say co-star Ashley Iaconetti brought up a Lake Tahoe trip Ashley and Amanda had taken. Ashley brought up drinking during the trip and that's when Josh snapped at Amanda and accused her of lying to him about not drinking.

Sources close to Josh, however, say their fight was about something "nasty" Amanda whispered in his ear that Josh felt disrespected him.

Josh ultimately left Amanda at the concert area and waited outside the venue. They broke up the next day.