UK intelligence agencies planned to spy on delegates to the Commonwealth heads of government meeting in 2009, including being asked to obtain information to give UK ministers an advantage in talks with their Commonwealth counterparts, according to a top-secret document seen by the Guardian.

The meeting, which takes place every two years, was held in Trinidad in 2009. The UK delegation was headed by the Queen, with Prince Philip also in attendance, along with Gordon Brown, the then prime minister, David Miliband, then foreign secretary, and Douglas Alexander, then international development secretary.

A page from an internal top-secret intranet of GCHQ, shared with the NSA, discovered by the 29-year-old whistleblower Edward Snowden and seen by the Guardian, shows a list of "key intelligence requirements" set out for the summit.

Alongside notes to check for threats against the security of the UK delegation during the visit, the document lists "Intelligence to inform UK senior's [sic] Bi-lats", "Initelligence [sic] on South Africa's views on Zimbabwe prior to Brown/Zuma meeting" and "climate change reporting".

The revelation that UK intelligence agencies made plans to target ministers and officials from Commonwealth countries, as well as the targeting of G20 officials disclosed elsewhere, is likely to raise tensions among the Commonwealth nations, who may seek clarity over whether their officials were bugged, and if so to what extent.

The note, which was prepared in advance of the meeting, also sets out a schedule for different UK agencies to set up their activities in Trinidad. MI6 were tasked to set up several days before the event, with GCHQ's operation beginning with the arrival of delegates. The Guardian is not publishing the original document as it contains logistical details and some limited references to personnel.

The 2009 Commonwealth meeting, which was also attended by Nicolas Sarkozy, then president of France, appears to have been the first time MI6 – formally known as SIS, or the Secret Intelligence Service – had been asked to gather intelligence from a Commonwealth heads of government gathering.

"SIS have no past history of targeting this meeting," the document notes in an explanation of why operations might be limited in their scope.

As it was prepared in advance of the Commonwealth meeting, the memo does not confirm to what extent surveillance was carried out, or even whether planned operations actually took place.

However, it does stress to agency staff that "we will be measured on our ability to deliver".

The memo also shows that the agencies were preparing to brief senior ministers, and the prime minister, during the conference.

The memo noted that Lady Kinnock was available for briefings from 25 to 29 November, David Miliband could be briefed from 26 to 29 November, and Gordon Brown on 29 November only.

There is no indication as to whether the briefings actually took place, or whether the ministers were aware of the security services' plans for the summit.