Former attorney general Dominic Grieve has said "egregious" behaviour like the CIA's interrogation of al Qaida suspects would not occur in Britain because of the European Convention on Human Rights.
The Conservatives have described their plans to stop British laws being overruled by European judges as "viable and legal".
Mr Grieve has criticised his party's proposals for a new Bill of Rights which proponents said would give UK courts and Parliament the final say over Europe.
He highlighted a report published recently by the US Senate which said waterboarding and confinement to a coffin-sized box for hours on end were among CIA techniques for interrogating al Qaida suspects.
Mr Grieve said: "This great state anchored in the principles of the rule of law nevertheless succeeded in committing such egregious violations of rights at a time when it was under pressure.
"Surely this is why there is a lesson to be learned for us, not because I think the UK Government is perfect in its actions.
"As attorney general I have often had to grapple with all sorts of difficult issues but we now have a framework where I venture the suggestion that sort of egregious behaviour would not occur whereas before, as we know from examples like the Mau Mau in Kenya, it almost certainly happened in a similar fashion.
"That for me is why the human rights framework we have is valuable; not because it is perfect, not because it needs to be viewed as written on tablets of stone, not because it cannot be improved."
The Conservatives have pledged to scrap the 1998 Human Rights Act, introduced under the Labour government, which incorporates the European Convention on Human Rights into British law.
A condition of membership of the group of states signed up to the Convention is abiding by the decisions of the European Court of Human Rights.
Mr Grieve told an audience in Belfast most cases referred to the court from the UK were not proceeded with. He said there was little appetite in Europe for further reform of the body but accepted there had been a problem with attempts to "micro manage" states.
He said understandable irritation at how the Convention could restrict governments acting in the public interest should not result in throwing the toys out of the pram.
"The danger for my party's proposals is that firstly it risks wrecking the operation of the Convention on a European-wide basis if we pull out, which I think would be the inevitable consequence of the proposals but moreover it will do it for delivering what seems to me to be astonishingly few benefits when you consider that my party is now sufficiently wedded to the principle of the Convention that they wish to see any British Bill of Rights incorporate Convention rights within it.
"But it is right to say that they want to dilute those rights in a number of key areas which I think are unacceptable."
Mr Grieve lost his job as the Government's most senior legal adviser during a reshuffle last summer. He had been one of the most vocal supporters of the Convention.