Powell allegedly drove a golf buggy from the Welsh team's Vale of Glamorgan Hotel and was intercepted by police at services just off Junction 33 of the M4.
The 28-year-old was arrested with another un-named man at 6am, with a police investigation into the incident now underway.
Powell's agent, former Lions and England prop Mike Burton, told the BBC that his player was "very sorry and embarrassed about what happened".
"Andy was disappointed and embarrassed to find himself in this position," added Burton.
"He does not excuse or condone drink driving in any form and it was a misjudgment.
"He is sorry and he will face up to it."