Dowsett was not named in Movistar's roster announced on Monday morning, and Millar announced via Twitter that he had not been selected by Garmin-Sharp just before the team made a formal announcement.
Millar withdrew from both the British national time trial and road race over the weekend suffering from a cough. Dowsett placed third in the time trial, behind Bradley Wiggins (Sky) and Geraint Thomas (Sky), but his team stated that he had been suffering from a 'breathing problems' since the Tour de Suisse.
It was to be Millar's final outing at the Tour before he retires at the end of the season and he had been told a week before that he was riding. He was then told late on Sunday night that he had not been selected after all.
Despite the home start, it's one of the lowest counts for the number of British riders on the Tour's start list in the past decade. Last year there were six.
There was discontent among fans last week when Wiggins - and then Team Sky - confirmed that the 2012 Tour champion would not be on the start line in Leeds.
Newly-crowned British road race champion Peter Kennaugh was also not selected by Sky to ride in the Tour, denying spectators the chance to see the red, white and blue striped jersey on home roads.
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