The Guardian has written to key Australian politicians of both main parties to seek their assurance that the incoming government will not intimidate journalists or hamper their work as the paper continues to investigate government surveillance around the world.

Last month at London's Heathrow airport UK authorities detained David Miranda, the partner of Guardian journalist Glenn Greenwald, who reported for the paper on the revelations made by former US National Security Agency analyst Edward Snowden.

It was subsequently revealed that threats of legal action from the British government had led the Guardian to destroy some computer equipment in London.

"These actions seem at least partly intended to intimidate and deter journalists and those who assist them in their work on this and related matters," Wednesday's letter, from Guardian Australia editor Katharine Viner, notes.

She wrote: "Although anti-terrorism and communications interception laws in Australia are not the same as the laws of the UK and US, the relevant Australian laws are open to misuse unless those responsible are vigilant. In some circumstances, for instance, if certain anti-terrorism provisions are used in relation to a journalist, he or she may be restrained by law from disclosing that fact itself."

The letter was sent to attorney-general Mark Dreyfus and his Coalition shadow George Brandis, foreign minister Bob Carr and his opposite number Julie Bishop, defence minister designate Mike Kelly and his Coalition shadow David Johnston, home affairs minister Jason Clare and his Coalition counterpart Michael Keenan, and communications minister Anthony Albanese and his opposite number Malcolm Turnbull.

Full text of the letter

3 September 2013

Parliament House

Canberra ACT 2600

Dear

I write to seek assurances from you in your capacity as one who is or may be, after the election on 7 September, responsible for Australian Government agencies that help to give practical form to the so-called Five Eyes intelligence sharing arrangements among the United States, United Kingdom, Canada, New Zealand and Australia. The agencies I refer to are the Australian Signals Directorate, Australian Security Intelligence Organisation, Australian Secret Intelligence Service and the Australian Federal Police.

The Guardian runs editorial operations in the UK, US and Australia and the behaviour of authorities in those countries can have a serious impact on its journalism.

Consistent with caretaker conventions in the current election campaign period, I am seeking assurances from relevant Government and Opposition MPs. Please note that I intend to publish the requests and responses.

You will be aware that since 6 June 2013 The Guardian has been reporting on aspects of the surveillance by the US National Security Agency and other entities of the phone, email, internet and social media use of members of the public inside and outside the United States. Other media organisations are also reporting on this and related matters. At its heart is the issue of the proper balance between liberty and security in democratic societies under the rule of law, and the effectiveness of the oversight of that balance.

In the US it has become apparent that a significant number of members of Congress have concerns about the extent of the surveillance and the adequacy of oversight.

A recently declassified ruling by the FISA court, which authorises the surveillance, demonstrates that court's concerns.

President Obama has said he welcomes a debate on this matter and to that end some relevant materials have been declassified by the Director of National Intelligence.

In the UK in recent times the authorities have taken at least two steps affecting The Guardian which have serious implications for The Guardian and for the freedom of the press more generally.

First, threats of legal action which may have constrained The Guardian's reporting of this matter in the UK led The Guardian to accede to the UK Government's insistence that The Guardian destroy some of our equipment in London so as to destroy information stored on it. This futile act – futile because copies of the information exist elsewhere - was carried out at The Guardian office in the presence of government representatives.

The second step by UK authorities was to detain at Heathrow Airport on 18 August David Miranda, partner of Glenn Greenwald, the Guardian US columnist and author of principal reports about the NSA surveillance. Mr Miranda, who was only in transit through the UK, was held for almost the maximum permissible nine hours; not told the identities of his interrogators; denied the implements necessary to make a copy of their questions; and unable to obtain legal advice until late in his detention. His property and the information it contained were seized.

A UK court has since placed limits on what the UK authorities can do with the seized material. The lawfulness of Mr Miranda's detention under a power aimed at terrorists has been challenged and is under investigation.

These actions seem at least partly intended to intimidate and deter journalists and those who assist them in their work on this and related matters. Grave disquiet has been expressed amongst the world's press. The essence of the disquiet is the harm the UK authorities' actions do to freedom of the press. While actions of this sort obviously disrupt the journalists against whom they are directly aimed, they can also affect other journalists reporting on the same or similar matters.

Yet such reporting, and the public debate that flows from it, are legitimate and necessary elements of the checks and balances on which democratic societies depend.

Its recent UK experience has led The Guardian to consider its two other operating environments, the US and Australia.

Several factors make it less likely that actions similar to those of the UK Government will be employed successfully against Guardian US. Among those factors is the American legal environment, in particular the First Amendment and relevant Supreme Court doctrine against prior restraint. Also, sensitivity in that country's robust journalistic culture is already high due to recent covert gathering of the phone records of several journalists at the Associated Press, an event which led the US Attorney-General to issue new guidelines on 12 July 2013.

The operating environment of Guardian Australia is different from the UK and US. Australia lacks an equivalent of the US First Amendment. Although anti-terrorism and communications interception laws in Australia are not the same as the laws of the UK and US, the relevant Australian laws are open to misuse unless those responsible are vigilant. In some circumstances, for instance, if certain anti-terrorism provisions are used in relation to a journalist he or she may be restrained by law from disclosing that fact itself.

And so for all these reasons I seek your assurance that Australian Government agencies will not, whether on their own initiative or on request from a foreign government, take actions to hamper or intimidate journalists in Australia as they go about their legitimate task of scrutinising the extent, lawfulness and oversight of government surveillance of the public's phone, email, internet and social media use.

Yours sincerely,

Katharine Viner, Editor, Guardian Australia, on behalf of Alan Rusbridger, Editor-in-Chief