But the Irish, knowing they needed a big margin of victory to stand any chance of capturing the title, repeatedly ripped through the Italian defense with D'Arcy, Dempsey, Horgan, O'Gara and Hickie all crossing the Italian line before the home team replied through Bortolami.
Hickie went over again with two minutes to go to stretch the Irish lead to 34 points before De Marigny's second try for the Italians in the third minute of injury time made the French task against Scotland a little easier.
After losses to Ireland, Scotland, Wales and Italy, the Welsh victory over England meant climbing away from last to leave Scotland with the "wooden spoon."
Gareth Jenkins team scored early tries through flyhalf James Hook and prop Chris Horsman but squandered a 15-0 lead as England hit back to draw level at 18-18 early in the second half.
Flyhalf Harry Ellis and winger Jason Robinson both scored tries for England but Hook landed two more penalties and a drop goal for a personal tally of 22 points to guide Wales to victory.
England wound up with three victories against two losses for a third place finish.