Eighteen months after Northwestern Mutual Life Assurance began exploring a sale of Russell Investments - and a year since London Stock Exchange agreed to acquire it for $2.7 billion - the future of its consulting and asset management arm is still up in the air.

Citic, a conglomerate based in China, has emerged as front-runner in a shortlist of bidders, according to people familiar with the situation. But an auction has faced a serious set-back, following the shock decision of previous favourite, consultant Towers Watson, to merge with insurance broker Willis.