Brian O'Driscoll scored Leinster's clinching try

Newport had started with real intent and pinned Leinster back in their own half early on, winning a penalty which Shane Howarth converted into three points.

But as in their two previous encounters this season in the Heineken Cup, both won by the Irishmen, Newport found that any sloppy play was ruthlessly punished.

Andy Powell gathered a kick through and ran back hard at the Leinster midfield.

The young No 8's lay-back was textbook but a stray Newport boot chipped the ball forwards into Shane Horgan's arms, who then raced in under the posts.

With Spooner adding the conversion for Leinster and then a penalty soon after, the alarm bells were ringing for the visitors.

Just after the quarter-hour Leinster scored a second try, when good vision from Spooner saw his cross-field kick gathered on the left by full-back Girvan Dempsey.

Spooner converted and struck another two points when wing Denis Hickie scored just a minute later.

Gordon D'Arcy received the ball from the restart and raced untouched up the right wing.

Lions centre Brian O'Driscoll was up in support, passed back inside to fellow centre Horgan, who then switched play out to the left to find the flying Hickie.

Andy Marinos was inspirational for Newport

At 24-3 down so early in the match, Newport could have been excused for letting their heads go down.

Instead they redoubled their efforts, with skipper Simon Raiwalui and former Springbok prop Adrian Garvey driving the Black and Ambers forward.

It was Garvey who was able to pop a pass out of two tackles to Newport's Irishman Matt Mostyn, who scored under the posts, converted by Howarth.

Newport blindside Peter Buxton was rightly sin-binned for deliberately killing the ball, but he had little choice after Powell had failed to deal with a loose ball.

Despite being a man short, the Welshmen marched back into opposition territory and scored a try through centre Andy Marinos.

Howarth drew two defenders and sent a long pass off his right hand, Powell dithered when he should have given the scoring pass but Marinos put his head down and went over in the corner.

Howarth's conversion was the last score of an entertaining half that left the tie nicely poised at 24-17 to Leinster.

Spooner had an early chance to put Leinster two scores clear but dragged his penalty kick across the face of the posts.

Howarth departed soon after with a hand injury to be replaced by Jason Strange, whose first contribution was a raking kick that drove Leinster back into their own 22.

Newport sucked in defenders before Strange sent the ball left after Garvey's charge, allowing replacement Matthew Watkins - on at wing, with Ben Breeze moving to full-back for the injured Matt Pini - to slide over.

Shane Howarth was forced off with an injury

Strange could have tied the scores had he not narrowly missed the conversion, but Spooner gave Leinster some breathing space with a penalty soon after.

For the first time in the match the slippery conditions got the better of the players, but eventually Leinster reasserted their dominance.

The Leinster forwards committed defenders in a series of driving rucks, creating space for O'Driscoll to race over the line after brushing aside Breeze's poor attempt to tackle.

Spooner added the extra points, but was forced to leave the field soon after with a nasty face wound caused by a stray Newport boot.

Marinos was denied a deserved try by a forward pass as the clock ticked towards injury time.

But Newport were denied even that small consolation, as Leinster pipped the Welshmen for the third time this season.

Leinster: Tries: Dempsey, D. Hickie, O'Driscoll, Horgan. Cons: Spooner 4. Pens: Spooner 2.

Newport: Tries: Mostyn, Marinos, M. Watkins. Cons: Howarth 2. Pen: Howarth.

Att: 7,300

Leinster: G Dempsey; D Hickie, B O'Driscoll, S Horgan, G D'Arcy; N Spooner, B O'Meara; R Corrigan (capt), S Byrne, P Wallace, L Cullen, M O'Kelly, E Miller, V Costello, K Gleeson.
Reps: P Coyle, G Hickie, B Casey, T Brennan, B Willis, P McKenna, A Magro.

Newport: M Pini; M Mostyn, A Marinos, J Pritchard, B Breeze; S Howarth, D Burn; R Snow, J Richards, A Garvey, I Gough, S Raiwalui (capt), P Buxton, G Gravell, A Powell.
Reps: C Anthony, P Young, M Voyle, J Powell, M Watkins, J Strange, L Lane.

Referee: Steve Lander (RFU).