Irish bookies Paddy Power closed their market on the former Bournemouth boss succeeding Lennon late on Thursday, with Howe having been at odds as short as 1/5 for much of the week.
Betfair followed suit after the 43-year-old was backed in at 1/10.
Howe, who spent most of his playing career with the Cherries, has been linked with the top job at Celtic Park since last year, having been out of work since leaving the Vitality Stadium following Bournemouth’s relegation at the end of the 2019/20 season.
Lennon's future as Celtic boss is in doubt after Wednesday night's 2-2 draw with Livingston. The Hoops are without a win in 2021 and the club’s hierachy are undertaking an urgent review of the Northern Irishman's performance with Rangers 20 points clear at the top of the table and Celtic’s ten-in-a-row hopes up in smoke.
The outcome of the review are not yet known but the fact that two bookies have suspended betting is likely to fuel rumours that patience with Lennon may have run out.
Howe hung up his boots in 2007 and went on to have two spells managing Bournemouth either side of a brief stint at Burnley. He led the Cherries to the Premier League in 2015 and a ninth-place finish in 2016/17 but left when they were relegated after finishing 18th just a point off safety last season.