Civil liberties campaigner Shami Chakrabati has called for an end to the "pit bull posturing of home secretaries who would be king".
Ms Chakrabati was a guest speaker at the Tory conference
In what appeared to be an attack on John Reid, she also criticised people willing to sacrifice civil liberties "on the high altar of ambition".
The Liberty director was speaking at the Conservative Party conference.
Mr Reid's tough-talking speech at last week's Labour conference was widely interpreted as a party leadership bid.
Ms Chakrabati, one of a series of guest speakers at the Tory conference in Bournemouth, said "fundamental rights and freedoms" were not the preserve of any one party but belonged to all the people.
Cautioning against abandoning hard fought-for civil liberties in the so-called war on terror, she said: "Free speech and fair trials were born in this country and rightly shared with the continent and the commonwealth and the wider world."
Mr Reid told the Labour conference last week that people needed to stand up to extremist bullies, pledging "we will never be brow-beaten by bullies".