He finished the tournament with a total of 24 under 264, thus breaking the PGTI record of 22 under for four rounds, set by Jyoti Randhawa in 2007.
Shamim Khan finished in second place at 18 under 270.
Lahiri's (65-65-67-67) final round 67 comprised six birdies and a bogey. Overnight leader by six strokes, he started slowly as he made par-bogey on the first two holes and followed that up with four pars from the third through the sixth.
Shamim, in the meantime, birdied the first, third and fifth to close the gap to two strokes.
Lahiri then got back into rhythm with the help of birdies on the seventh, ninth, 11th and 12th to open up a five-stroke lead.
He made a couple of excellent chips on the seventh and ninth and then sank some long putts on the 11th and 12th holes. The Bangalore-based golfer finally coasted to his third professional win after making birdies on the 14th and 17th. In the process, the 22-year-old also broke the course record of 21 under for four rounds, set by Gaganjeet Bhullar in 2009.
"I really enjoyed playing at Aamby Valley as the greens here are perhaps amongst the best in the country. I'm quite pleased that the dry spell I have had in 2010 has finally come to an end with this victory. Hopefully, this win would get the ball rolling for me for the rest of the year," said Lahiri.
He added, "I was a little shaky at the start even as Shamim was quite aggressive. I had to change my game-plan once Shamim started closing the gap. I also started attacking the pins as a result of this change in game-plan. Finally, it was my solid putting that helped me sail through. I putted the best in the last round."
Delhi's Shamim Khan (71-66-66-67) finished second at 18 under 270, thanks to a final round of 67 that featured six birdies and a bogey.
Abhishek Jha of Bangalore was third at 12 under 276 while Delhi's Ashok Kumar ended up fourth with a total of 11 under 277.
Gurki Shergill of Pune finished tied 15th with a three under 285 total.
Aditya Bhandarkar of Pune, the only amateur to have made the cut, won the amateur title as he totaled 12 over 300. Bhandarkar finished tied 48th.
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