Sue Garner, head of the school admissions and class size unit at the Department for Education and Skills, was talking at a conference in London when she cited the London Oratory, where three of Tony Blair's children attended.
Ms Garner said the school's intake would be changed by the introduction of choice advisers, which all local authorities must employ by 2008. Some areas are already trialling such people.
The advisers will offer independent advice on school admissions to low-income families and are an important part of a government drive to close social gaps.
Ms Garner said an analysis had shown that the London Oratory's intake fairly reflected the backgrounds of those who applied for places but the school's reputation put people off applying unless they were high achieving and middle class. "Choice advisers would prevent some parents thinking that this school is not for the likes of us," she said.
But local authority admissions officers complained that the advisers were adding to bureaucracy and might do little to help parents.
Tim Pollock, school admissions manager for Somerset County Council, said lack of funds meant just one adviser had been appointed for the whole of his county on a salary of less than pound;20,000. She had to rely on his admissions team for details of phone calls for parents and for technical advice, creating more work.
"The introduction of choice advisers needs a lot more thought," Mr Pollock said. "I am in favour of more advice, but it has only made the situation worse.
"Admissions officers are under a duty to give independent advice. So why does the Government think we're not independent?"
Ms Garner appeared upset by the admissions officers' responses and told them to stop asking her questions "if this is going to be about beating me up".