Bradley Wiggins closed in on a maiden Tour de France title but had to deal with controversial behaviour from team-mate Chris Froome which some saw as patronising on the final mountain stage.

Spaniard Alejandro Valverde won the 17th stage, with Froome coming home second 19 seconds back and ahead of Wiggins who retained the overall leader's yellow jersey with a lead of two minutes five seconds over his Sky team mate.

Froome looked the stronger of the two Britons on the final climb to Peyragudes and could not resist pulling ahead several times, leaving Wiggins stranded, before conspicuously looking back and gesturing to his compatriot to keep up.

"I do not like what Froome did. It could devalue Wiggins's victory," said Laurent Jalabert a former world champion and Vuelta winner.

With the Tour title almost in the bag, a gracious Wiggins, who looks poised to become the first Briton to triumph on the French roads, would not be drawn into a controversy.

"Chris said he wanted to go for the stage and I said yes. We weren't too sure of the time gaps," Wiggins said.

"The moment we crossed the Peyresourde, I allowed myself to drift and that was the first time I thought maybe I've won the Tour today.

"All the way up that last climb my concentration had gone, everything about my performance had gone. Chris was egging me on...and I was in another world, really."

Froome, kept on a tight leash by Team Sky directors to support Wiggins, had already given into temptation in the Alpine stage to La Toussuire, attacking a group featuring his leader before being reined in by sports director Sean Yates.

"It was the plan to do the job to retain the yellow jersey, to protect it," said Froome, who finished second in last year's Tour of Spain ahead of Wiggins.

"Everybody makes sacrifices, (British Team Sky rider Mark) Cavendish makes sacrifices everyday, everybody in the team makes sacrifices for the yellow jersey, it's cycling, it's our sport."

Team principal David Brailsford also tried to defuse the controversy, saying: ''I was encouraging them, I think it was another hard day in the last mountain stage. We made a big step towards victory in the Tour de France.''

Asked if Wiggins had effectively secured the title, he said: ''Normally, barring an accident, but there are stages to come and the closer you get (to Paris) the more you have to be vigilant.''

Italian Vincenzo Nibali retained third place overall despite being dropped in the final kilometres and now sits 2:41 off the pace before Saturday's final time trial, which will heavily favour Wiggins and Froome, and Sunday's finish in Paris.

WHITE JERSEY

Friday's 18th stage is a slightly hilly stage that should not change the hierarchy.

American Tejay van Garderen kept the white jersey for the best under-25 rider even though he was dropped by his closest rival, France's Thibaut Pinot, in the 15.4-km climb to Peyragudes.

Before the final kilometres, Wiggins had been barely tested by his rivals with Nibali's Liquigas team doing most of the work in front of the peloton in the last two ascents to secure their leader's spot on the podium.

Defending champion Cadel Evans, who surrendered his crown when he cracked in Wednesday's stage to Bagneres de Luchon, had another bad day, finishing 2:10 off the pace.

Nibali tried briefly, though. The Sicilian jumped away on the first ascent of the day to join a group of fugitives, but he was talked out of it by Valverde as his presence would have prompted Team Sky to chase hard.

France's Thomas Voeckler featured in the breakaway and virtually secured the polka dot jersey for the best climber.

World champion Cavendish escaped apparently unhurt from a crash with some 55 kms left, with team mate Richie Porte also falling off his bike.

The Australian needed treatment on his left arm before riding his way back into the peloton before the start of the climb to the out-of-category Port de Bales.

As the main bunch started the ascent, Liquigas upped the pace, gradually stretching out the peloton.

Valverde went solo 3.5 km from the top of the Port de Bales as his former breakaway companions were dragged back.

The Spaniard, who came back from a two-year doping-related suspension this season, benefited from Froome's obligation to wait for Wiggins and stayed ahead until the line.

- Reuters