Amnesty International is calling for technology companies to observe users’ rights to privacy and freedom of expression.

The human rights charity has ranked the quality and strength of privacy levels offered by different online messaging services.

Facebook and Apple are among the companies ranked the highest, while Tencent and Snapchat were given lower privacy scores.

Amnesty International said it is concerned about how compromised privacy online impacts on activists’ abilities to communicate with each other.

The group says all online messaging services should be encrypted, so that only the sender and recipient can read them.

Executive director of Amnesty International Ireland Colm O’Gorman said Skype was also lacking in some areas of protecting users’ messages.

“Disappointingly, despite Microsoft’s strong policy commitment on human rights, it’s still using quite a weak form of encryption on Skype. It only scores 40 out of 100.

“None of those companies are using end-to-end encryption for their users’ communications.

“Snapchat, which many people use, also scored badly, despite having a strong policy commitment towards privacy. In practice, it’s not doing enough to protect privacy.”