Wasps rallied from 13-0 down to score 30 unanswered points with two tries from Paul Sackey and scores from James Haskell and Josh Lewsey to keep alive their hopes of a league and European Cup double.

But it proved a nightmarish day for Ashton who will not have any Wasps or Leicester players available for the first Test in South Africa on May 26.

The England pack which started against Wales in the final RBS 6 Nations game was made up entirely of players from Welford Road and Adams Park.

England’s director of rugby Rob Andrew confirmed last week that no player appearing in the Heineken Cup final will be considered for the Test in Bloemfontein six days later.

Ashton is also likely to be without his Bath contingent after their thrilling 31-30 European Challenge Cup semi-final victory over Saracens.

Red Rose problems aside, Wasps’ victory set up a final between the two most successful club sides in English rugby over the last decade.

Wasps return to Twickenham, where they won the 2004 Heineken Cup, while Leicester are chasing a third European title – a feat only Toulouse have achieved.

But early on it appeared as if Northampton were ready to pull off another major upset after their quarter-final victory over Biarritz.

The Saints, bottom of the Guinness Premiership with just one game remaining to save their skins, surged ahead inside four minutes.

Sean Lamont crashed through the Wasps defence and Robbie Kydd ate up 30 yards before being felled by Dominic Waldouck.

The ball was recycled quickly and Carlos Spencer slipped a pass out of the tackle for Reihana to score in the corner and then land a tricky touchline conversion.

Wasps went in search of an immediate reply but a promising move ended with Tom Palmer spilling a simple pass and Lawrence Dallaglio clashing with Spencer.

The Wasps captain was furious and appeared to accuse the former All Black of an eye gouge, though referee Alan Lewis took no action.

Wasps were at sixes and sevens, conceding penalties at the scrum and the breakdown which allowed Reihana to boot the Saints into a 13-0 lead after a one-sided opening quarter.

Tom Voyce sparked Wasps back into life with a dart down the left wing and Danny Cipriani then combined expertly with Joe Worsley for what appeared a certain try. But Reihana did just enough to disrupt Cipriani’s dive and, in a carbon copy of last weekend, he touched the ball down on the in-goal touch-line.

Wasps continued to make good ground when they ran at Northampton and were were rewarded five minutes before the interval when Sackey squeezed over in the corner.

The England winger juggled the pass from Reddan but reclaimed it to score in the corner, avoiding the touchline on this occasion.

Mark Van Gisbergen, whose penalty had finally got Wasps on the board after 27 minutes, curled his conversion attempt wide.

If the scowl on the face of coach Shaun Edwards was anything to go by, the Wasps players had been given a fearful rocket at half-time.

They began the second period with pace, power and purpose, winning a scrum against the head and then driving deep into Northampton territory.

Saints flanker Ben Lewitt was forced to kill the ball under his own posts and was sin-binned for his troubles, allowing Van Gisbergen to boot Wasps within two points.

Northampton had defended the sin-bin period well but just as time was ticking down Cipriani booted Wasps into the Saints 22.

Wasps attacked from the back of the lineout and Haskell drove over to score with his first touch of the ball after replacing Dallaglio. Van Gisbergen’s conversion hit the post but Wasps led for the first time in the game and never looked like relinquishing their advantage.

Josh Lewsey had replaced Waldouck shortly after half-time and was making a major impact in midfield.

Sackey ran onto his scissors pass and then powered through four defenders to extend Wasps’ lead to 10 points with just 10 minutes remaining.

Any hope Northampton had of a comeback were effectively ended when Lewitt crashed into Sackey after he had touched down, earning Wasps a penalty from kick-off.

Wasps booted play right back into Saints territory and Lewsey put the icing on the cake with Wasps’ fourth try in the corner after a powerful drive forward from Tom Rees.