A block on 'blasphemous' tweets was lifted by Twitter this week following a protest by humanists and secularist organisations.

The block had been in place since May 18 after Pakistan requested Twitter bar any tweets deemed to denigrate Islam or those that were "blasphemous" or "unethical".

It was the first time Twitter had used its Country Withheld Content Tool in Pakistan, according to the ChillingEffects website, which said there had been five requests to Twitter from the Pakistan Telecommunications Authority.

The action taken by Twitter was strongly criticised in a letter signed by the British Humanist Association, American Atheists, and the Richard Dawkins Foundation for Reason and Science among others.

In the letter, part of their #TwitterTheocracy campaign, they said they were "deeply disturbed" to learn that Pakistan was demanding censorship in line with its blasphemy laws.

The signatories said blocking tweets because they might be offensive to the religious feelings of Pakistani Muslims was a "violation of basic human rights" under Article 18 of the United Nations Universal Declaration of Human Rights.

"However, it is also denying one of the most basic elements of modern human civilisation: communication. As a

consequence, Pakistan is only serving to hamper its own development as a society," the letter read.

"The rights to follow one's conscience, to express one's beliefs and values, and to exchange ideas with others are foundational to human well-being, and must be granted to all for a society to advance.

"The proper response to speech that one finds offensive is not censorship, which leads to suppression and civil violence, but more speech.

"The ability to think freely, to have doubt, to investigate doubt, and to arrive at new conclusions, advances our shared communities.

"To survive and flourish, we must learn to civilly discuss important matters, including and especially religion. True political and economic stability depends on openness, and falls quickly in the face of censorship."

BHA's head of public affairs, Pavan Dhaliwal, welcomed the reversal on the block, saying: "It should not have taken a public campaign for Twitter to see sense and end its bizarre collusion with suppressors of free speech, but we are nevertheless pleased that it has now changed its policy on this matter.

"According to the annual IHEU Freedom of Thought Report, Pakistan is one of thirteen countries where apostasy is punishable by death, and in Pakistan's case this is only because it sets an extraordinarily low bar and an obscenely high penalty for infractions of its strict blasphemy code.

"We call on Pakistan to revise these laws in accordance with the international treaties it is part of."