The letter references extensive Herald reporting on the issue, notably a number of suspicious burglaries in February of Brady's home and campus office, and claims last month her car had been sabotaged in response to her work exploring China's activities in New Zealand.
The 169 signatories comprise a global swathe of academic sinologists, former diplomats and journalists for international news outlets, including Australian public intellectual Clive Hamilton, US Council on Foreign Relations fellow Elizabeth Economy , and Paris-based Jean-Philippe Béja, a researcher at the elite National Center for Scientific Research.
Prominent journalists who signed the letter include Jamil Anderlini, the Hong Kong-based Asia editor for the Financial Times, and Jonathan Mirsky, the former China correspondent for the Observer.
Letter organiser Martin Hala, a Prague-based academic who runs the Sinopsis project tracking China's activity in the Czech republic, said Brady was widely-respected in her field and it was important to express solidarity.
"She's been a towering figure in contemporary Chinese studies, and her research has been groundbreaking," he said.
Hala said China's push-back against criticism in western countries had to date been limited to propaganda and buying influence, and the apparent escalation to criminal harassment was concerning.
"This is a worrying trend, and if we don't raise our voices in support of Anne-Maire, then any one of us could be next."
Anderlini, who stressed he signed the letter in a personal capacity, has worked overseas for nearly two decades but grew up in Wellington.
"I am a New Zealander and care very much about the future of my country. Professor Brady - one of the most respected sinologists in the world - has raised some very worrying claims in her work," he said.
Anderlini said the contrast between the domestic and international import given to Brady's groundbreaking "Magic Weapons" paper published last September - which outlined China's influence activities in New Zealand - was concerning.
"The reaction so far from many in New Zealand has been to dismiss her, to ignore her, and to say 'It'll all be okay, mate,' even as people in other countries take her claims very seriously. And, frankly, that's not good enough."
Prime Minister Jacinda Ardern's response to the affair to date has been cautious, refusing to comment on the burglaries and car sabotage by saying it was a matter for police, declining to cite China's influence as a problem for New Zealand, and issuing only generic support for academic freedom in response to earlier open letters.
The Herald broke news in September that the February burglaries of Brady's home and office now involved the NZSIS, Police and Interpol and had stretched on for months. Last month it was revealed Brady's mechanic suspected her car had bene sabotaged, widening the investigation.
A police spokesperson yesterday said Brady's car had been inspected and "the police investigation is ongoing".
The latest letter comes after calls for Government action on the issue have built steadily in recent weeks, with international media beginning to weigh in on the issue and tensions in the China-New Zealand relations coming to a head.
Two weeks ago 29 academics and human rights activists - spearheaded by Amnesty International's New Zealand office - wrote to Ardern and Foreign Minister Winston Peters urging action.
This was soon followed by 35 of Brady's colleagues at the University of Canterbury co-signing a letter saying they took the apparent criminal harassment "very seriously" and urged the Government be transparent in its investigation of the affair.
This week the nations' political scientists passed a motion at their annual conference in Wellington affirming academic freedom, with president and Victoria University associate professor Kate McMillian saying: "Political studies is an area in which academic freedom is particularly sensitive ... and academics need to be able to research and to contribute to public debates openly and with confidence."
Over the weekend The Times of London dedicated a full page in their Sunday edition to the Brady affair, saying Brady's Christchurch home and office at the University of Canterbury was the scene for "a tale of espionage, sabotage and geopolitical intrigue".
The pressure comes as government agencies and diplomats struggle to balance the trade and security concerns in New Zealand's relationship with the rising People's Republic of China.
Last week the government spy agency, the Government Communications and Security Bureau, blocked Chinese tech firm Huawei on national security grounds from being involved in upgrading New Zealand's mobile phone infrastructure.
And the Prime Minister's office last week confirmed - following news breaking in the Herald - that a long-discussed visit in 2018 by Ardern to China would not take place.
