John McIntosh, the headmaster of his sons' school, the formerly grant maintained London Oratory, chose the run-up to the conference to appeal to parents for voluntary contributions to make good a pound;250,000 shortfall in the school's budget.
He thus reawakened a row that ministers thought they had resolved when they allowed GM schools to remain semi-independent and provided extra funds to cushion the effects of the change to aided or foundation status.
He also presented the Prime Minister with an acute personal dilemma: whether to pay the pound;45 a month requested by the school (pound;30 for one child and pound;15 for a second), thus appearing to concede that the school was under-funded, or to appear mean.
Labour ministers were furious at the timing of the request. Graham Lane, education chairman of the Local Government Association, accused Mr McIntosh, a former Tory education adviser, of playing politics on the eve of the Labour conference.
Opted-out schools still received extra funding at the expense of all other schools, he said. "If he cannot administer his budget, that is his problem."
Mr Blair himself said headteachers were entitled to send letters to parents asking for voluntary contributions but that it was "wrong in principle ...for people to be put under any pressure to pay for their children's education."
Teacher unions and spokesmen for the former GM schools issued warnings about the emergence of a two-tier education system, in which middle-class schools would be able to charge parents to keep up standards while schools in poorer areas could not.
David Blunkett, the Education Secretary, said a two-tier system was not on the cards and the Government would ensure all schools were equally and fairly funded. He announced a review intended to restrict ways in which state schools solicited money from parents.
Another issue Labour would like to feel it has buried - the continued existence of selective schools - was in the news again this week.
Mr Blair said he was not waging a vendetta against the remaining 164 grammar schools, threatened by Labour legislation allowing for parental ballots on their survival. "I just don't think it's the issue for us," he said. "It's not the thing that motivates me greatly."
He was speaking shortly after the campaign had been launched in Ripon to end 450 years of grammar school education in the city, which looks set to incite a bitter struggle.
At the Labour conference itself, Chancellor Gordon Brown unveiled plans to extend the Government's New Deal programme for the unemployed into the next Parliament, although he said 18- to 24-year-olds who repeatedly turned down offers of work could lose all their benefits under a tightening of the rules.
He held out the prospect of full employment and an end to child poverty within a generation but warned that his vision would be wrecked if he bowed to demands to increase public spending before the next election.
On the same tough note, education secretary David Blunkett in his speech on Wednesday attacked families who condone truancy.