The PCC formally investigated the complaint, which arose after the tabloid published a picture of Ms Middleton on March 29th taken under circumstances amounting to harassment.
A public statement was issued the next day by the Mirror on page two.
"Kate Middleton has made repeatedly clear to the press – through the Commission, to photographers, and to editors directly – that she objects to being followed by photographers when she is on her own going about her daily business and there is no specific public interest reason for following her," the PCC statement said.
Under the code of practice photographers must not pursue people – whatever their fame or status – once they have been asked to stop. Media editors are responsible for ensuring material used from photographers complies with this code.
Since Prince William and Ms Middleton began dating at the University of St Andrews there has been intense media interest in their relationship.
Efforts to clamp down on intrusion into her life have become especially important in the wake of the paparazzi furore which surrounded Prince William's late mother, Princess Diana.
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