When American International Group agreed a deal to sell its prized Taiwanese insurance asset to a Hong Kong-based consortium in October, the deal was hailed a success for the troubled US insurer and its quest to repay billions of dollars of US taxpayer money.

China Strategic, a little-known Hong Kong battery maker, and its partner Primus Financial, a start-up investment group headed by former Citigroup Asia boss Robert Morse, agreed to pay $2.2bn to buy Taiwan's Nan Shan Life Insurance from AIG. It would be Taiwan's largest financial-sector deal involving a foreign acquirer, eclipsing Standard Chartered's $1.2bn takeover of Hsinchu International Bank in 2006.

But less than two months on and the deal has been swept up in a political storm that highlights the difficulties faced by dealmakers working within the greater China region.