The 17-year-old winger is currently one of England's hottest prospects and was being chased by a host of Premier League clubs looking to secure his signature, but none managed to strike an agreement with either club or player.
Arsenal boss Arsene Wenger publically expressed his interest in Oxlade-Chamberlain towards the end of January, much to the annoyance of Cortese who believes the Emirates Stadium supremo was out of order by attempting to unsettle the young midfielder.
"It definitely did not help their cause," the Swiss said in the Telegraph. "We focused on what we wanted to do and not what others wanted to do. I was in the driver's seat. There was not a second I doubted that he would stay."
Cortese was left unimpressed by the methods deployed by Oxlade-Chamberlain's suitors and cited that as the main reason he was unwilling to part with Saints' prized asset during January.
"I have experienced a lot of things over the past month about the behaviour of some Premier League clubs," he added.
"Some have really behaved very well. There has been professionalism and there has been the complete opposite as well.
"Some simply sent a fax. No communication, nothing. It gave the impression that they didn't care about the boy. Those faxes went straight into the bin. The others made a phone enquiry and I said I didn't want to get involved in negotiations."
The South Coast outfit are hoping to hang onto their latest prodigy until the end of next season.
"We care about the boy," said Cortese. "I believe that for Alex the best place for him to progress over the next 18 months is here."
But having seen fellow stars Theo Walcott and Gareth Bale depart for Arsenal and Tottenham Hotspur in recent seasons, that may prove easier said than done.
By Matt Kenny
