Cavendish, who won four stages in 2008 and six in 2009, claimed his third win of the 2010 Tour with a sprint victory on the 184.5-kilometre 11th stage from Sisteron to Bourg-les-Valence.
But the 25-year-old lost Renshaw for the remaining nine days of racing after the Australian was disqualified for three times using his head to push Team Garmin-Transitions rival Julian Dean, a New Zealander, out of his line.
Cavendish won by a comfortable margin, with Alessandro Petacchi (Lampre-Farnese) second and Tyler Farrar (Team Garmin-Transitions) third, but his hopes of winning the points classification title receded with Renshaw’s removal.
Dean, who veered from the right of the road to the left, was aiming to lead Farrar to the finish line, but the New Zealander was adjudged to have been impeded by Renshaw in the finishing straight.
Cavendish accelerated off Renshaw’s wheel to record a win by three bike lengths which saw him move 29 points adrift of the green jersey.
Petacchi assumed the maillot vert after Thor Hushovd (Cervelo Test Team) finished seventh yesterday.
But Cavendish, who was not disciplined for the incident involving Renshaw, was left subdued after his team-mate’s punishment.
“I’m very sad,” said Cavendish.
“We came around the last corner in a good position, Bernie (Bernhard Eisel) went to lead it out, then Mark (Renshaw) went, but Julian Dean came round the right, hooked his elbow over Mark’s right, Mark used his head to get away, but it (Dean’s line) put everybody behind in danger.
“Mark gave us a bit of space which kept everyone upright.”
Cavendish, who claimed 35 points for the win to move to 132 points overall, suggested HTC-Columbia might appeal the race commissionaires’ decision.
He said: “We understand the commissaires have made a decision, we’ll have to see how the situation evolves.
“The commissaires have made the decision, we don’t necessarily agree.
“We don’t believe the same, but we’ll see what happens.”
However, officials seem set to rebuff any appeal, comparing Renshaw’s tactic to the physical exchanges in keirin track racing.
Tour technical director Jean-Francois Pescheux said: “Renshaw is out. We watched the film once and it was blatant. He head-butted Dean like in a keirin race.
“This is a bike race, not a gladiator’s arena. Everybody could have ended up on their backs.”
Petacchi’s second place — and 30 points — means he overtook Hushovd after the Norwegian finished seventh to claim 19 points.
Italian Petacchi now has 161 points, Hushovd is second with 157, Robbie McEwan (Katusha) is third with 138 and Cavendish is six points further back in fourth place.
Whether Italian Petacchi and McEwan survive the Pyrenean peaks to come remains to be seen and there appears set to be another titanic struggle between Hushovd and Cavendish for the points title.
Today’s 210.5km 12th stage from Bourg-de-Peage to Mende features five classified climbs and is unlikely to be won by a sprinter.