Leigh Halfpenny’s wayward boot allowed Leinster to strengthen their grip at the top of the RaboDirect PRO12 table after a nervy climax against Cardiff Blues.

Leinster, who after this 23-19 win now hold a nine-point lead at the top of the Rabo standings, threatened to blow away the hosts early on when Sean O'Brien and Rob Kearney both went over to give the visitors an early 14-point advantage.

Two Halfpenny penalties and a Gethin Jenkins try brought the Blues back into the contest.

But with the stage set for a crucial scalp for the Welsh region Welsh international full-back Halfpenny crucially missed two penalties in quick succession just after the hour mark.

With just a point between the sides Leinster’s Fergus McFadden then kicked Joe Schmidt’s side past the winning post with a penalty 13 minutes from time.

The Blues, who had Gavin Henson withdraw before kick-off with a calf injury, went behind in the fifth minute when No. 8 Jamie Heaslip fed O’Brien to crash under the posts.

Fly-half Jonathan Sexton added the extras before Kearney went over for his side’s second try three minutes later – Sexton again kicking the conversion for a 14-0 lead.

Welsh international Halfpenny began the fight back on 17 minutes when he booted his first penalty, and followed that up three minutes later with another.

Fly-half Dan Parks – retained in Andy Robinson’s Scotland Six Nations squad despite suggestions otherwise – then got in on the act with a drop-goal before Sexton’s three-pointer just before the break sent Leinster in 17-9 ahead.

Halfpenny’s third penalty of the contest 11 minutes after the restart seemed to galvanize the Blues, as prop Jenkins then barged over from close-range to reduce the deficit still further.

The full-back’s subsequent conversion brought the Blues to within one point. However the wheels then fell off for the 23-year-old as he missed two glorious opportunities to snatch the game.

His 63rd minute penalty fell short, and he then screwed another wide two minutes later as the chance of a remarkable comeback slipped away with it.

Outside centre McFadden then showed him how to do it as he extended Leinster’s winning league run to ten games.