Boff said he had never expected everyone in the party to share his views, but said there was “a profound difference” between disagreeing with someone and “deciding their beliefs disqualify them from even putting themselves forward to serve”.
He added: “A political party that cannot tolerate support for fundamental human rights has moved a very long way from the principles that first attracted me to it.
“I have not abandoned my Conservative principles. I believe the party has abandoned some of its own.
“I will not surrender those principles in order to remain a member of any political party.”
Hall said of Boff: “Andrew has been a forthright and vocal supporter of Conservative principles, and we thank him for his contribution to our party.”
The ECHR was a treaty drawn up by the Council of Europe after World War Two. It is separate from the EU and unrelated to changes after Brexit.
It sets out rights such as the right to life, a fair trial, freedom of expression, and the right to family life, and it bans torture and degrading treatment.
Cases go to the European Court of Human Rights in Strasbourg. Since the Human Rights Act 1998, UK courts can also apply the convention directly.
The only European countries not part of the treaty are Russia, which was expelled in 2022, and Belarus.
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