O’Sullivan caused play to be temporarily suspended when appearing to loosen the tip on his cue after returning to his chair while leading 22-21.

Dott cleared up to win the frame with a superb 66 break but O’Sullivan immediately left the Crucible arena to carry out repairs with the aid of fellow professional Jimmy Michie from Pontefract.

O’Sullivan, who has used more than 20 tips during the past fortnight, came back after a 15-minute delay during which time Dott had been in the practice room.

And ironically the two-time world champion immediately compiled his best break of the tie, a 124 clearance to the final black, to edge 8-7 ahead.

Dott held his nerve to draw level in the next with a composed 74 after O’Sullivan had broken down on 49 to end the session all square.

He punched the air with delight after making sure of the frame and, although he then shook hands with O’Sullivan, Dott turned his ahead away from his rival and clearly looked perturbed at how events had unfolded.

O’Sullivan did not look comfortable before the tip controversy and asked for a noisy spectator to be moved before the mid-session interval although he was later allowed back into the auditorium.

O’Sullivan had been given snooker’s equivalent of a yellow card for swearing in a previous match with Ryan Day.

Snooker legend and now BBC pundit Steve Davis slammed the tactics employed by the Londoner, who had looked uneasy all through the session.

Six-times world champion Davis said: “It looked like Ronnie was picking at the tip to get it off.

“It is unfair on Graeme Dott who has just started to hit some rhythm. In other sports can you deliberately halt progress? Is there a precedent for saying ’you should lose a frame?’

Another former world champion in John Parrott echoed Davis’ sentiments and said: “Let’s say the tip got help in coming off. I am not very happy with that. He should not be allowed to do that.”

O’Sullivan, who defeated Dott in the 2004 final, had been fortunate to eke out a 5-3 overnight lead after being guilty of several mistakes.

And the world number one was still not firing on all cylinders as he found himself on the receiving end of more determined play and consistent break-building from Dott who had a knack of winning the scrappy frames.

O’Sullivan was well ahead in the first frame of the session but failed to escape from two snookers behind the black on the final pink and Dott edged home after 35 nervy minutes.

Dott was first amongst the balls in the next with a run of 68 but O’Sullivan looked as if he could pinch the frame before breaking down on 38 attempting the final red down the rail.

His dogged opponent won his fourth frame in the row after O’Sullivan, who was already well in arrears, failed to convert an attempted plant. A run of 23 to the black by Dott put him ahead for the first time since he had led 2-1.

O’Sullivan finally managed to stop the rot in the last frame before the mid-session interval with a 62 to the final pink but he left the arena with plenty to think about.

O’Sullivan won a scrappy 13th frame before the bizarre antics in the next over-shadowed proceedings.