International human rights lawyer Amal Clooney will help launch a British-Canadian move to protect journalists from attacks and restrictions around the world, say ministers.
She has been appointed co-chair of a judicial body to make proposals to counter the laws that hinder reporters.
"Those with a pen in hand should not feel a noose around their necks," the British-Lebanese lawyer told a G7 foreign ministers meeting on Friday in France.
Ms. Clooney said it has "never been more dangerous to report the news".
"According to the Committee on the Protection of Journalists, we have detained the largest number of journalists in the last five years since their records began more than three decades ago," she added.
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According to Reporters Without Borders, more than 60 journalists were killed in 2018, more than half of them deliberately targeted. The murder of Saudi columnist Jamal Khashoggi was condemned internationally in particular. British Foreign Minister Jeremy Hunt told the event that democratic states must become "an international taboo of the highest order" in order to assassinate, arrest or arrest journalists for their work.
Hunt, who appeared alongside his Canadian counterpart Chrystia Freeland, also called Clooney a special envoy for media freedom.
"If journalists are unable to challenge those responsible, hold them to account freely and with impunity, they begin with a slippery slope to the closed societies that none of us wants to influence," he said.
"The media plays a vital role in bringing the powerful to justice. The fact that worldwide laws on the Draconic and Outdated are being used to restrict the ability of the media to report the truth can not be prevented.
"Amal Clooney's leading work in the field of human rights means that she is ideally positioned to ensure that this campaign has real impact for journalists and the free societies that depend on their work." The wife of Hollywood lawyer George Clooney said she had been "honored" given the role.
Last year, Clooney joined the attorney team, which included two Reuters journalists who were sentenced to seven years in prison under the official secrets of Myanmar.
On Friday, she said only one in ten countries have a free press.
Regarding the murder of Khashoggi, she said, "Many more such crimes are not reported and too many are not punished."
Her experience in defending journalists in countries such as Egypt and Myanmar "has shown me how vaguely vague laws and corrupt courts can be used to silence dissent and disguise the media."
In December last year, Clooney chased US President Donald Trump's "green light" against regime to prosecute journalists for his anti-press rhetoric.
She added that she could propose reforms of national laws that run counter to international standards such as blasphemy laws and urge governments to grant consular protection to journalists abroad. The proposals are not legally binding.
Khashoggi's death sparked global outrage, but human rights groups criticized the reluctant response of many Western capitals, many of which signaled the importance of trade relations because they had not taken a tougher stance on Saudi Arabia.