It was the first Dauphiné stage victory of Porte's career as he proved too fast in the 23.5-kilometres individual time trial from La Tour-du-Pin to Bourgoin-Jallieu.

The BMC Racing Team rider finished in front of German world champion Tony Martin.

Martin, of Katusha-Alpecin, finished 12 seconds behind Porte while Movistar's Alejandro Valverde of Spain completed the top three, 24 seconds off the pace.

"I didn't expect to win today and certainly not by this much onto the other general classification contenders," said Porte.

"I really worked hard on my time trial this year.

"I hadn't ridden any time trial for a long time, so I'm really happy with what I did today.

"Of course it's always nice to win races.

"Winning a time trial probably gives even more confidence."

Despite Porte's emphatic victory, Belgium's Thomas De Gendt retained the overall race lead.

Porte is the Lotto-Soudal rider's nearest challenger but sits 27 seconds back.

Valverde moved into third place in the general classification, 51 seconds behind De Gendt.

Three-time winner Chris Froome of Team Sky is 1:04 behind after the Briton crossed the line in eighth place today.

Action at the International Cycling Union WorldTour event is due to continue in France tomorrow with stage five.

Competitors will race a 175.5km route from La Tour-de-Salvagny to Mâcon.