Auckland Mayor Len Brown was advised by his former mistress Bevan Chuang to speak English and not to try speaking Mandarin on an official trip to Hong Kong, papers show.
"Please do not say 'ni hao' [hello] or 'xie xie' [thank you] in Hong Kong, as this is Mandarin and this will make Len look foolish," she told mayoral press secretary Melanya Burrows.
The mayor's then-lover offered the advice two days before Mr Brown flew out to China and Hong Kong on a New Zealand Transport Agency trip to study big infrastructure projects in November 2011.
Official documents about the four-day trip were released to the Weekend Herald last night under the Official Information Act.
They back up the findings on an EY (formerly Ernst & Young) investigation which raised concerns about a "private" and/or "personal" dinner Mr Brown had with an interpreter at the Okura Garden Hotel in Shanghai on November 11.