It is the second time in six months that the 19-year-old has changed coach after she parted company with Zeljko Krajan to work with Maclagan just prior to the grass-court season.
She reached the last 16 of Wimbledon and third round of the US Open under his guidance, but a run of just three wins in four tournaments has seen Robson decide that another changed was needed.
BBC tennis correspondent Russell Fuller said: "Robson informed Maclagan in a telephone conversation at the weekend that she wants to try a fresh approach in 2014: her enthusiasm to extend the relationship waned as she experienced a recent disappointing run of results in Asia.
"Croatia's Davis Cup captain Zejlko Krajan questioned Robson's work ethic when they parted company in the spring. Maclagan is a very different personality, so the 19-year-old must now consider very carefully who she does think can best harness her talent, and help improve her consistency away from the Grand Slams."