British Lions scrum-half Phillips scorched over in the 51st minute with the decisive score following a quick line-out by Wales skipper Matthew Rees.
However the try was surrounded in controversy as Rees threw in a ball which he received from a ball boy. The laws of the game state a quick throw-in must be with the same ball which was put into touch. The correct ball was still being retrieved by Shane Williams when Phillips was racing down the touchline.
Number eight Ryan Jones also reached the milestone of 50 appearances and the pair were given the honour of leading their team-mates out at a sold-out Millennium Stadium.
Brian O’Driscoll handed Ireland an early lead but Wales fought back as Phillips’ try and 11 points from man of the match James Hook sealed a third successive win ahead of next weekend’s trip to Paris.
Wales’ championship hopes were handed a boost by France’s shock 22-21 defeat in Italy.
Warren Gatland’s men were given another lift when Eoin Reddan was forced off in the first minute after the Ireland scrum-half took Lee Byrne’s kick full in the face.
Peter Stringer replaced the Leinster number nine but it had little affect on the visitors who flew into a third minute lead. Tommy Bowe spotted a gap in the Welsh defence and the Ospreys wing supplied O’Driscoll with the try-scoring pass.
It was a historic try for the Irish captain as he equalled Ian Smith’s 78-year record of 24 championship tries. Ronan O’Gara added the conversion for a 7-0 buffer and also celebrated passing 1,000 Test points.
The Dragons lost Craig Mitchell to injury in the 12th minute to a shoulder injury with John Yapp called into action. But, despite the loss of the tight-head prop, Wales responded.
And, after Hook saw his 17th minute penalty crash against the right-hand upright, the fly-half went one better two minutes later.
Hook then trimmed the deficit to just one point on 28 minutes before O’Gara restored Ireland’s four-point advantage with a second penalty.
Wales rallied and Leigh Halfpenny hit a 45-metre penalty but O’Gara notched up his second penalty to put Ireland 13-9 ahead at the interval.
O’Gara departed for Jonathan Sexton on 50 minutes but Wales took the lead for the first time in the match moments later when quick thinking by Rees set Phillips free.
The Ospreys star flew past Stringer and beat the cover from Bowe to touchdown. Hook converted and then added a 68th minute penalty to steer Wales to victory.
