LEINSTER 6 NEWPORT 10, Donnybrook
Scorers: Leinster: Pens: Fergus McFadden 2
Newport: Try: Matthew Pewtner; Con: Chris Wannell; Pen: Chris Wannell
Leinster made an encouraging start in bitterly cold conditions and were nearly awarded a penalty but Fergus McFadden's effort, two minutes in, fell agonisingly short of the uprights.
Powerful separate surges from Eoin Sheriff and Ian Madigan in the opening ten minutes failed to reap points, and a 40-metre break by Stephen Keogh in the 14th minute almost finished in the game's first try, but the Leinster skipper was denied by the Welsh defence.
A knock sustained in the ensuing ruck ended Keogh's evening and in the 19th minute Newport took the lead from a penalty by out-half Chris Wannell after an infringement at a ruck inside the Leinster 22.
The visitors pressed and some clever sniping around the fringes from the aptly-named scrum half Andrew Quick led to their second penalty of the evening in the 27th minute, though Wannell's effort fell wide into the Bective end.
Leinster regrouped and despite McFadden's second penalty effort, three minutes later, missing the target, a spell of solid pressure ensued for the home side.
Newport right winger Mike Poole was sent to the sin-bin in the 35th minute for successive deliberate infringements and though Leinster held the upper hand until the interval, a difficult injury-time penalty from McFadden could not level the scores.
Replacement scrum half Paul O'Donohoe entered the fray for the second period and carved through the Newport midfield in the 42nd minute.
From the resulting spell of forward dominance, McFadden added his side's first points of the evening with a penalty.
Leinster's ascendency was halted when lock Devin Toner was sin-binned for an off-the-ball incident and Newport benefited from the one man advantage with left winger Matthew Pewtner touching down in the corner after a slick back-line move.
Wannell added the difficult conversion to extend Newport's lead to 10-3 after 51 minutes.
The game ebbed and flowed with neither side asserting themselves but with five minutes remaining McFadden slotted home his second penalty after Leinster gained dominance at a scrum.
A wayward Wannell penalty in the 77th minute failed to extend Newport's advantage, but they held on to seal the win thus ensuring a tense finale in the final round of pool games.
Leinster will travel to Scotland to face Gael Force in the province's final Pool A encounter on Wednesday, March 10.
LEINSTER: Niall Morris; Michael Keating, Eoin O'Malley, Fergus McFadden, Simon Keogh; Ian Madigan, Chris Keane; Ronan McCormack, Richardt Strauss, Mike Ross, Trevor Hogan, Devin Toner, Eoin Sheriff, Paul Ryan, Stephen Keogh (capt).
Replacements used: Jordi Murphy for Stephen Keogh (17 mins), Paul O'Donohoe for Keane (half-time), Stan Wright for McCormack (50), Shane Monahan for Morris (68), Jason Harris-Wright for Strauss (70), Kyle Tonetti for Keating (80). Not used: Ciaran Ruddock.
NEWPORT: Gareth Wyatt; Mike Poole, Adam Hughes, Pat Leach, Matthew Pewtner; Chris Wannell, Andrew Quick; Dai Pattison, Duane Goodfield, Gethin Robinson, Dafydd Rosser, Adam Brown, Sam Waldron, Craig Hill, Andrew Coombs (capt).
Replacements used: Lewis Evans for Waldron (49 mins), Andrew Brown for Goodfield (58). Not used: Dan Way, Mark Workman, Scott Williams, Dan Griffiths, Kyle Barrett
Referee: Keith Lewis (England)