Victory over relegation-fighters Brighton also saw the Foxes achieve a new club record of 26 league wins in a season, beating the previous record set in their 1956/7 promotion campaign.
But it was Brighton who almost stole a shock lead after four minutes when Paul Brooker ran onto a Gary Hart throughball with Ian Walker having to beat out his 20-yard drive before killing the ball at the second attempt.
But it was Leicester who ignited another sell out Walker's Stadium crowd to take the lead in the 10th minute when Paul Dickov received the ball wide on the left and cleverly jinked his way beyond Danny Cullip, before crossing for Izzet to glance home a diving header.
Matt Elliott then drove just wide from 22 yards and Stewart curled a 25-yard effort over the angle of post and bar before Brighton almost snatched a 38th-minute equaliser.
Bobby Zamora knocked down Kerry Mayo's deep cross to the far post into the path of Paul Watson, whose rising shot from 16 yards seemed destined for the back on the net until Ian Walker intervened with a brilliant flying save.
But it was City who doubled their advantage a minute before half time when man-of-the-match Izzet swung over a corner for Stewart to head powerfully into the roof of the net from five yards out.
After the break City went close early on with Trevor Benjamin firing narrowly wide from 18 yards and Dickov scooping a 15-yard effort onto the roof of the net.
On the hour mark a superb flick by Stewart saw the midfielder race beyond Mayo to cross from the byline for Benjamin to fire in a close-range shot which Dave Beasant did well to keep out.
James Scowcroft went closest to putting the icing on the cake when he shot against a post in the final minute, but nothing was going to spoil the promotion party for the jubilant Leicester players who celebrated after the final whistle with champagne and a lap of honour.