The Evening Standard reports that the Conservative Party has emailed councillors and activists alerting them to Blair's appearance on LBC today.
"The Prime Minister is dong a phone-in between 10-11am tomorrow on LBC97.3FM. We would like our supporters to phone in and question him. Obviously he is vulnerable on Hutton and tuition fees," the email says.
The newspaper says that the email also carries a briefing paper and the words "Please DO NOT pass to the media".
Labour communications director David Hill immediately questioned whether or not the email, described as "dirty tricks", had been sanctioned by Tory leader Michael Howard.
The Tories denied that it was authorised by Howard but said that it was something that any campaign team would do and that it stood by the move.
A Conservative spokesman said: "Any effective campaigning organisation encourages its supporters to be active and to make their views known and there is nothing wrong with reminding our supporters that the Prime Minister is taking part in a heavily trailed radio interview."
Labour emailed its own members today asking them to tune in and hear Blair speak.
Since Howard took control of the party late last year he has reorganised the communications and marketing departments, appointing advertising guru Lord Maurice Saatchi as co-chairman to improve the way it is run.
The Press Complaints Commission's Guy Black has been recruited as Howard's press secretary and the party began the year with a one-page manifesto published in national newspapers outlining Howard's personal beliefs.
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