"The confidence is still there - we're still the champions and that means something," said Phillips.
"France are a good side so it's going to be immensely tough. But we've got to go there with belief and play some rugby.
"We've got to cut the mistakes out and the penalties out and have the belief."
Tries from Simon Zebo and Cian Healy saw Wales trail 23-3 at half-time against Ireland, with the deficit then extended to 27 when Brian O'Driscoll's converted score saw Ireland hit 30 just three minutes after the restart.
But Wales responded superbly and crossed for three tries of their own through Alex Cuthbert, Leigh Halfpenny and Craig Mitchell as they came within a whisker of an incredible comeback.
The contrast in performance in each half couldn't have been more marked and Phillips admits Wales need to produce their latter showing right from the off next weekend.
"We've got to get desperate. When we get desperate we tend to play better. We've got to start desperate and have that edge about us from the word go," added Phillips.
"We've got to look at how it got away from us in the first half. We gave away a lot of penalties and didn't really get our hands on the ball. We had too many turnovers and couldn't get started. We were off the boil with too many errors and too many penalties. We couldn't get a foothold in the game.
"It's about having that confidence from the start and backing ourselves, coming out of our shells earlier in the game. We've got to really go for it - it's as simple as that, really.
"We've got to start better, test them fitness wise and play some more rugby. We've got to play with no fear from the start."
You can follow all of the action for France v Wales at http://www.wru.co.uk/live