KP had even blamed Cook for his ouster from the English team and has always questioned Cook's leadership. He is often seen criticises the southpaw batter on social media platforms.
Recently, the South Africa-born cricketer found support in former Australian cricketer Shane Watson on micro-blogging site Twitter to attack Cook, following announcement of England's Test team against Pakistan.
Watson was apparently shocked with the exclusion of Ian Bell from the Test squad and wrote to Pietersen, "@KP24 I really want to know why @Ian_Bell isn't being recalled to the Test team. A beautiful batsmen with a great record#class#22Hundreds."
The flamboyant England batsman utilised the opportunity and trolled Cook with a harsh tweet.
"I reckon Cook won't pick anyone that could jeopardise any of his records, Watto! 😂 @ShaneRWatson33," wrote KP.
Cook recently broke Sachin Tendulkar's record and became the youngest cricketer to complete 10000 Test runs.
Even former England cricket skipper Nasser Hussain, earlier, said that he would have picked in-form wicketkeeper-batsman Jos Buttler over Gary Ballance for England's first Test against Pakistan at Lord's starting on Thursday (July 14).