The Irishman’s contract was due to expire at the end of the current season and with Neil Warnock bringing in his own coaches, Robbie has decided to leave the club with immediate effect.
The club would like to place on record its thanks to Robbie for all his hard work and wish him well for his future in coaching and management.
Boro becomes the 17th stopping point for the 71-year-old, who first cut his managerial teeth at Gainsborough Trinity back in 1980.
The first of his eight promotions came in 1987 when he guided Scarborough into the Football League. Two more followed at Notts County when he guided them from the third tier to the top division in successive seasons and he also oversaw success at Huddersfield Town and Plymouth Argyle.
He enjoyed an eight-year stint at his boyhood club Sheffield United that culminated in him leading the Blades back to the Premier League in 2006, where they stayed for one season before Warnock resigned after they were controversially relegated.
His next job saw him save Crystal Palace from relegation to the third tier, but he was soon back on the promotion trail, leading Queens Park Rangers to the Premier League.
His most recent success came at Cardiff City where he led the Bluebirds to the Premier League in 2018.