The 26-year-old Englishman beat former Open champion Paul Lawrie by two shots after leading for much of the tournament, shortened to 54 holes due to thunderstorms on Friday.

But Poulter nearly threw it away on the long 17th when he three-putted for bogey to Lawrie's birdie to allow the Scotsman to leapfrog him into a one-shot lead.

Lawrie, though, proceeded to carve his drive out of bounds on the 18th tee on the way to a double bogey as his playing partner Poulter made birdie for his third title.

Poulter, champion in Rome in 2000 on his way to earning the Rookie of the Year title, finished on 19 under par after a closing round of 69.

"Unbelievable," said Poulter, the 2001 Moroccan Open winner, who was using a putter lent to him by Justin Rose.

"I'm just so happy I hit a good drive on 18.

"It was unfortunate that Paul hit his out of bounds but thankfully it was enough.

"This is absolutely fantastic because I hadn't won this year and I've made it my goal to win every year on tour.

"I've done that throughout my pro career and this keeps me going forward and bettering myself all the time."

Lawrie began the day a shot behind but the lead changed hands several times before Poulter, who fired a hole-in-one in a first-round 61, forced a one-shot lead going down 17.

A downhearted Lawrie, who held his nerve to win the Open in a play-off at Carnoustie in 1999, said: "I thought I hit a pretty good swing on the last and it came off at an unbelievable angle right.

"I would have bet my house on making four up the last."

Denmark's Anders Hansen (66), local favourite Emanuele Canonica (70) and England's Anthony Wall (65) were locked in third on 15 under.

Ireland's Padraig Harrington needed a top-four finish to overhaul the absent Retief Goosen at the head of the Order of Merit.

Harrington climbed from joint 34th overnight with a stunning 63 but had to settle for a tie for sixth.

The Italian Open is the penultimate event of the season but the last for players hoping to finish in the top 115 on the Order of Merit and retain their Tour cards for next year.