Lighting on Sir Kenneth Calman's assertion that he would continue to eat beef, Ms Harman said the real question was whether the Chief Medical Officer would give beef to his grandchildren. She suggested that parents on the Spongiform Encephalopathy Advisory Committee had stopped doing so.
"The time has passed for false reassurance," said Ms Harman. And she called for an end to the type of photocall in which John Gummer fed a beefburger to his young daughter.
In an unusual move, two Cabinet ministers - Stephen Dorrell and Douglas Hogg - made separate statements to MPs. Mr Dorrell, Secretary of State for Health, disclosed that 10 deaths from Creutzfeldt-Jakob Disease - the human equivalent to mad cow disease - appeared to be linked to exposure to BSE before the 1989 offal ban. Mr Hogg, Agriculture Minister, announced further action to stop infected material entering the food chain.
Still more unusually, both ministers pointedly refrained from joining Tory backbenchers in accusing Labour of "scaremongering" and damaging the beef industry.
Harold Elletson, MP for Blackpool North, asked Mr Dorrell to condemn "extreme vegetarian, anti-farming activists like Ms Harman who are now campaigning to stop children eating meat".
Paul Marland, a farmer and chairman of the Tory backbench agriculture committee, urged ministers not to over-react.
Neil Hamilton, MP for Tatton, urged ministers not to forget "the lesson of the salmonella in eggs fiasco some years ago where an incautious word from a minister devastated an industry for no proven benefit to the health of the nation".
The refusal of ministers to play party politics lent weight to the assertion by David Hinchliffe, Labour MP for Wakefield, of "a growing realisation by the Government that we could be facing horrific health problems in future years".
Pressed by Glenda Jackson, Labour MP for Hampstead and Highgate, to give "stronger advice" to schools and parents about the dangers of small children being fed beef, Mr Dorrell said it was precisely because he understood the sensitivity of that issue that he had asked SEAC for specific advice. "I'm a parent of two young children," he reminded the House. He accepted that parents would be concerned but said there was no evidence of age sensitivity.
Mr Dorrell said previous scientific advice had been categoric that there was no possibility of BSE entering the human food chain. "But it is precisely to guard against the possibility that there may be a link that the various controls were introduced."
Explaining the need for the new controls and further research, Mr Dorrell said work at the government surveillance unit in Edinburgh on 10 cases of CJD in people under 42 had identified a previously unrecognised and consistent disease pattern. "There remains no scientific proof that BSE can be transmitted to man by beef, but the committee have concluded that the most likely explanation at present is that these cases are linked to exposure to BSE before the introduction of the specified offal ban in 1989."
Mr Hogg assured MPs concerned about the beef market that support mechanisms existed within the Common Agricultural Policy and the situation would be monitored closely. But he said the best opinion was that beef and beef products could be eaten with confidence and he would continue to eat it.