Ronnie O'Sullivan accused referee Olivier Marteel of "looking for trouble" as the six-time champion took a 5-3 lead over Judd Trump in the World Championship final.
The world number one was given a formal warning by the Belgian for a gesture made in the final frame of the session.
The argument that followed overshadowed the end of a captivating first session.
"I get a vibe with the guy," O'Sullivan told Eurosport. "He just seems to be looking for trouble."
O'Sullivan added: "They have got hundreds of cameras out there. I am not having any of it because I think he is trying to create something."
Marteel, who is taking charge of his second world final, reprimanded O'Sullivan for making what he believed to be an obscene gesture, prompting the player to challenge the official to check the camera.
Trump went on to win the frame but also appeared irritated by the timing of an incident that came with it delicately poised.
O'Sullivan fist-bumped Trump but left the arena without offering Marteel a customary acknowledgementO'Sullivan had earlier complained about a security guard who was moving in his line of sight during the third frame, and he was also involved in a lengthy exchange with the referee over the placing of the white following a miss in the fourth frame, at one point suggesting Marteel should play the shot himself.
The 46-year-old is already facing an investigation by the WPBSA disciplinary committee for allegedly making a lewd gesture after missing a black in the 13th frame of his 10-5 first-round win over Dave Gilbert.
O'Sullivan wins five frames in a row before Trump rallies
Trump, the 2019 winner, won the opening frame with a composed break of 72 but was then rocked as O'Sullivan took over with two superb centuries and a break of 68 to reel off the next five frames.
Trump, who saw his table time limited, responded with a 97 and held his nerve to reduce his arrears in a tense conclusion to the session.
O'Sullivan's failure to get position on the yellow and subsequent foul gave Trump, who had failed to convert chances of his own and was guilty of some poor shot selection when given a free ball, a reprieve and he appeared delighted as he left the arena.
O'Sullivan, who is eyeing a record-equalling seventh world crown in the modern era, won the opening session of the 2020 final against Kyren Wilson before running away with the match 18-8.
Trump's ability to limit the damage felt important particularly after appearing rattled by gifting O'Sullivan the fourth frame of the afternoon, missing a red, yellow and green before conceding a free ball and losing on a re-spotted black.
Their final resumes on Sunday evening at 19:00 BST.
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