Hilde Haugsgjerd, Executive editor-in-chief of Aftenposten, along with three other editors of Nordic titles have published the letter in today's Observer newspaper. The media quartet said there is "deep concern" that recent events in Britain potentially threaten press freedom.
David Miranda, the partner of the Guardian's Glenn Greenwald, was detained by British police for nine hours last week in Heathrow Airport en route to Brazil. The Brazilian citizen had his laptop and other personal items seized after being held under terror laws.
Greenwald has previously written several exclusive stories about US intelligence agencies using material leaked by National Security Agency whistleblower Edward Snowden.
In an extract from the letter they write; "We are surprised by the recent acts by officials of your government against our colleagues at the Guardian and deeply concerned that a stout defender of democracy and free debate like the United Kingdom uses anti-terror legislation in order to legalise what amounts to harassment of both the paper and individuals associated with it."
Haugsgjerd, together with Bo Lidegaard of Denmark's Politiken, Peter Wolodarski of Sweden's Dagens Nyheter and Riikka Venäläinen of Finland's Helsingin Sanomat, add in the letter that it is "deeply disturbing" that British police have since announced a criminal investigation.
They added; "The implication of these acts may have ramifications far beyond the borders of the UK, undermining the position of the free press throughout the world.
The four leading editors concluded their opinion editorial calling on Britain's Prime Minister to "reinstall your government among the leading defenders of the free press and an open debate in accordance with the proud tradition of your country."
The news comes in the wake of reports that the American National Security Agency are unsure how much data Snowden took as he has covered his digital tracks. Snowden is currently in Russia where the government has granted him asylum.