A report from a public health observer at the Trans-Pacific Partnership talks speaks despairingly about the efforts of international experts to ‘‘have language adopted to ensure that any nation that adopts strong tobacco control legislation is not sued or at risk’’.

‘‘Australia is and has been a constant stumbling block,’’ the memo says. ‘‘I totally understand the desire to avoid language that implies that Australia’s position under current law is weak or language that implies additional protection is needed,’’ the document says.

‘‘But what I am really trying to understand is what appears to be Australia’s resistance to any language on tobacco, and its seeming lack of interest in working on language that would protect Australia and others from future tobacco trade-based litigation.’’

Australia has required tobacco products to be sold in plain packages since last December. Attempts by companies including Philip Morris to overturn the law were defeated in the High Court. But it is now trying to sue Australia in the United Nations Commission on International Trade Law using an investor-state dispute settlement clause in an obscure Australia-Hong Kong agreement.

Most of the 12 nations taking part in the Trans-Pacific Partnership talks want to protect their rights to enact similar legislation in the face of a US insistence that the agreement include clauses allowing private corporations to sue governments.

‘‘I never thought Australia would be a major problem in this effort, but we repeatedly hear that it is, and that it is not interested in working on language that makes clear the strength of Australia’s current position while clarifying clearly and unambiguously that no nation that adopts strong tobacco control laws should be subject to the threat of litigation,’’ the email says.

Australia’s Trade Minister Andrew Robb has indicated he is prepared to trade Australia’s previous opposition to investor state dispute settlement clauses in exchange for greater access to markets for commodities such as sugar. He returned from the talks on Tuesday.

An Australia Institute survey released on Friday finds only 11 per cent of Australians ‘‘definitely know’’ about the Trans-Pacific Partnership negotiations.

Almost 90 per cent think the details of such deals should be made public before they are signed.

Told that the US wants the right for its corporations to sue governments, 75 per cent are opposed.

Asked whether they trust the Australian government when it says it will not sign an agreement which will push up the price of prescription drugs, 67 per cent say no.