Lambert struck in bizarre fashion in the third minute of stoppage-time at the Liberty Stadium when Swansea captain Ashley Williams's attempted clearance looped over home goalkeeper Michel Vorm and the ball went in off the Saints substitute's back.

Victory took Southampton to a tally of 55 points, six more than ninth-placed Newcastle, with just one league game remaining for both clubs.

But even though Manchester United suffered a 1-0 loss at home to Sunderland on Saturday, the seventh-placed faltering champions could no longer be overhauled by the Saints given they are five points in front of Mauricio Pochettino's men.

Although defeat would have been a disappointment for Swansea caretaker boss Garry Monk, the former Swans defender is still in line to be made the Welsh club's new permanent manager having already overseen Swansea's successful campaign to retain their top-flight status after replacing the sacked Michael Laudrup in February.

Southampton produced the few moments of quality that illuminated an otherwise highly forgettable clash in south Wales, with England World Cup hopeful Luke Shaw repeatedly threatening the home defence.

Lambert was left out of Southampton's starting line-up following a buttock muscle problem, but was on the bench.

Monk made one change following last Saturday's 4-1 win against Aston Villa as Dutch international Dwight Tiendalli replaced Angel Rangel, out with a groin injury.

Swansea went closest to scoring early on when Pablo Hernandez's shot was well-saved by Artur Boruc, before Wilfried Bony glanced a header wide.

However, it was not long before the Saints started dominating territory and possession, although their attacking play lacked a cutting edge, with a free-kick from Dejan Lovren narrowly clearing the bar and Sam Gallagher wastefully heading too high.

Southampton captain Adam Lallana, like Shaw pushing to be included in England manager Roy Hodgson's squad for the World Cup, tested Vorm with an angled shot early in the second half.

But he was replaced with 30 minutes left by Lambert, while Monk sent on Nathan Dyer in place of Jonathan de Guzman as Swansea went in search of a third successive home league win following victories over Villa and Newcastle.

Lambert though had the last word as Southampton maintained their impressive form under Argentinian boss Pochettino.