Temasek's stake in Standard Chartered, which is worth around £2.3bn, forms part of a portfolio worth around £30bn.
The company has rarely been out of this year's financial pages, making headlines last month when it bought shares in Thai telecoms firm Shin Corp from the family of prime minister Thaksin Shinawatra. The £1bn sale triggered a crisis – Thaksin was not charged tax and middle-class voters revolted, prompting Thaksin to announce that he will step down.
Square Mile's role will be to highlight the role of the holding firm, which acts as a long-term asset management operation rather than running the companies in which it has invested. It will also highlight its policy of disclosure.
Temasek has drafted in the former head of Hill & Knowlton Singapore, Myrna Thomas, as corporate affairs managing director.
Square Mile MD Iain Bailey will head the account, reporting to Temasek corporate comms director Eva Ho.