Cabinet minister Ruth Kelly has complained to the Press Complaints Commission about the Daily Mirror's coverage of her son's private schooling.
The Communities Secretary said she felt the paper breached her son's right to privacy by disclosing that she was the minister who had taken a child out of the state system.
"After careful consideration I have decided to refer the Daily Mirror to the Press Complaints Commission, following their coverage of my son's schooling on 8th January," she said in a statement last night.
"My sole concern throughout has been the welfare of my young son. I believe his right to privacy has been breached.
"I have no intention of commenting further or drawing any further attention to this issue for the same reason."
Daily Mirror editor Richard Wallace said: "We are aware of Ruth Kelly's complaint to the PCC and we look forward to vigorously defending our position.
"We are confident that it was entirely right and proper that we identify Ms Kelly so that the public could decide whether her actions were appropriate – given that they were clearly at odds with Government policy."
The Daily Mirror was the first paper to disclose that Mrs Kelly – a former Education Secretary – was the minister who had enrolled a child at a £15,000-a-year private school.
The story was first reported, without names, in the Mail on Sunday.
The disclosure that the minister in question WAS a former Education Secretary caused anger among Labour MPs, some of whom accused Mrs Kelly of hypocrisy.
Following the criticism, Mrs Kelly disclosed that her son had "substantial" learning difficulties and that she was acting on professional advice.
In an emotional plea for understanding, she insisted she had to do the "right thing" for her child.
She also stressed that she would not be seeking to take advantage of any taxpayer-funded help available, and added that her other children would remain in the state sector.
Tony Blair has made his support for Mrs Kelly clear, and appeared with her at a Downing Street summit on Tuesday morning.
His official spokesman also said that the Prime Minister supported the right of parents to make choices about their children's education based on their needs, "irrespective of who their parents are or what job they do".
But Labour backbencher Ian Gibson said it sounded like "preferential treatment".