Six Nations - Controversial Wales try beats Ireland
Phillips raced over unopposed in the corner after a quick throw-in from captain Matthew Rees, sparking a furious protest from the Irish team who said the ball thrown in was not the one that had been kicked out.
Television replays showed they were correct but, after consulting with his touch judge, referee Jonathan Kaplan awarded the try. The rules of rugby stipulate that a quick throw-in can be taken only if the ball used is the one that went into touch.
Welsh fly-half and man-of-the-match James Hook, who won his 50th Welsh cap, said he had not seen the incident.
"To be honest, I had moved to the backs and looked up and Phillips was running down the wing," he told the BBC. "I didn't see it but maybe they (Ireland) have got a point. Let's all have a look at the video."
Ireland captain Brian O'Driscoll scored the only other try of the match, his 24th in the championship to equal the 78-year-old tournament record set by Scotland's Ian Smith.
Flyhalf Ronan O'Gara became the fifth player to pass 1,000 points in international rugby before he was substituted by Jonathan Sexton.
Ireland had a chance to tie the match in the final minute when the ball was spun wide to replacement fullback Paddy Wallace who had winger Keith Earls outside him with a clear run to the line.
But Wallace, who was perhaps thinking of giving Sexton an easier chance at the conversion which would have ensured a draw, stepped inside where he was enveloped by a grateful defence.
The win was Wales's third of the season, after they had opened the championship by losing to England, and their first at home since March last year.
They can still win the championship outright if they defeat France in Paris next weekend and England slip up against Scotland at home on Sunday and Ireland away next week.
"The boys were superb," Hook said. "We have trained really hard. Two wins on the road and this win here, we go to France with confidence."