Andrew Mitchell, who resigned from the Government over the “Plebgate” row, spoke out after David Cameron used his speech to the Conservative Party conference earlier this month to announce plans to scrap the Human Rights Act and replace it with a British Bill of Rights if he wins the next election.
“I think you should all be very careful with a generation of politicians who play fast and loose with the ancient liberties of this country, which our forefathers fought for,” Mr Mitchell said.
“The time of greatest shame in my Parliamentary career was when Parliament discussed whether people could be detained for 90 days.
“The idea that in Britain you can lock somebody up for 90 days without charging them is absolutely extraordinary.
“I remember not long ago on June 6 - the 70th anniversary of D-Day - where politicians were trumpeting what we fought for in World War Two, it was also the day that it was announced there would be a secret court in Britain.
“We do not live in a community where we have secret trials. Remember when you give powers to the state you give powers to people like us with our prejudices and preconceptions.
“And I think as a generation we should be very, very wary of giving up these ancient liberties, characterised sometimes as ‘British values’, which today’s politicians play too fast and too loose with.”
Mr Mitchell added: “We are a generation of politicians who have never had to fight a major war like our fathers and grandfathers had to do.
“That’s why I say with some passion do not let politicians give away these ancient liberties which have characterised the nature and values of our society.”
Mr Mitchell was speaking at the Cheltenham Literature Festival at an event chaired by Liberty director Shami Chakrabarti.