The Home Office memorandum says that when comment is "unavoidable", politicians should restrict themselves to revulsion, sympathy for victims and families, and the determination of the authorities "to leave no stone unturned in bringing the perpetrators to justice".
But Michael Howard issued a statement yesterday morning, on Conservative Party notepaper, saying Labour was not to be trusted on terrorism.
He said that one day, Marjorie Mowlam, the shadow Northern Ireland spokeswoman, said Sinn Fein could be invited into talks within weeks of a Labour election, then yesterday, following Aintree, the shadow Home Secretary, Jack Straw, contradicted her.
"In the same breath, Mr Straw says that a Labour government would fully operate the powers in the Prevention of Terrorism Act.
"Yet these are the very powers that Labour have voted against year after year in the House of Commons ... It is this kind of contradiction that makes it impossible to trust Labour on terrorism or any other subject."
Gordon Brown, the shadow Chancellor, protested on BBC radio's World this Weekend: "I think that all decent people will regret the fact that when there should be an all-party consensus to fight terrorism, Michael Howard has degenerated into making personalised and inaccurate comments about the Labour Party."
The Home Secretary's attack contrasted markedly with the neutral line taken by the Prime Minister in an interview on BBC television's Breakfast with Frost.
John Major said he had not had any discussions with the Labour leader over recent days, but he added: "I think the detestation of this sort of action, I think that's universal across the political divide."
Paddy Ashdown, leader of the Liberal Democrats, said of the Aintree incident: "This is a pointless, stupid act which will only make people in this country more angry and more determined to ensure that, whatever the IRA does, it will not be able to bomb its way into the election campaign or change the parties united policy on Northern Ireland."Reuse content