Team Sky placed third, 22 seconds behind winner Sunweb, with Tom Dumoulin, and BMC Racing. They covered the 42.5-kilometre course, which included a 1.4-kilometre climb, in 48-12 minutes and averaged 52.905kph.
"It's the worst time trial I've ever had in my life," Thomas told Cyclism'Actu.
He lost pace on the climb along with Owain Doull. Sky pushed on with the minimum four men: Froome, Vasil Kiryienka, Michal Kwiatkowski and Gianni Moscon.
"I really do not understand what happened, and from the start I felt it was not going well and I was not going to have a good time," Thomas added.
"I just did not have the legs: I suppose these are things that happen sometimes and you have to accept it."
The Welshman is returning from two major setbacks, crashing and abandoning both the Giro d'Italia and Tour de France this 2017 season.
Thomas won the opening time trial stage of the Tour in Düsseldorf and wore the yellow leader's jersey for four days. A crash in stage nine, however, broke his collarbone and forced him to withdraw.
He admitted that his comeback in the Tour of Britain was "pretty tough going." He told the Telegraph, "I feel like I'm lacking a bit of the punch for the finals, so I said I'd ride a bit [on the front] today. And get a bit of extra work done."
“The guys did their best effort and at the first split they were up by a second," Sport Director Brett Lancaster said of the Bergen time trial.
"We waited a bit on the climb as we knew ideally we needed five guys for the end, but the guys did a super job to bring it home."
Thomas wants to return in 2018 to race for a Grand Tour title. He began the Giro as Sky's leader with Mikel Landa.
"It's something I still want to give another go," he said.
"I feel like I am getting better each year. I take a lot of confidence out of the fitness I had before the Giro – I was doing the best numbers I'd ever done and that gives you confidence in training."
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