The lead was doubled four minutes later when Steve Naismith lashed home and the contest was essentially wrapped up in the seventh minute thanks to Lafferty’s second – a sidefooted finish from close range.
Nikica Jelavic, who supplied Lafferty with his second, made it 4-0 in the 49th minute with a nice finish from a free-kick and when Lafferty added the fifth for his hat-trick, it was party time for the visiting ‘Gers fans.
Kilmarnock grabbed a consolation goal in the 65th minute through James Dayton but it was nowhere near enough to deny the Glasgow giants from powering to their 53rd league title to send Smith in great style with his 10th SPL victory as manager of the club.
After the match, Smith tried to play down talk that the triumph was all about him, preferring to share the joyous occasion with all involved.
"Everything you do is for the club," he told Sky Sports.
"I'm just delighted that Rangers have managed to win. I'll have a wee drink just now, I think.
"I think in the end they (the players) deserved it - obviously I'm biased but I think they deserved it."