Singapore's Temasek defended its money-losing exit from Bank of America , saying the U.S.-centric bank did not fit its investment criteria and the risk was perceived to be greater than the expected return.

The explanation, a rarity for the state investor, came in a letter to major Singapore newspapers after the loss on BofA attracted fierce criticism from the usually muted pro-government local media, investors and independent blogs, which noted BofA shares have rallied more than 70 percent after Temasek's exit.

The losses are also expected to be discussed when Singapore's Parliament convenes next week.

Temasek, which is headed by Ho Ching, the wife of Singapore's prime minister, sold its 3 percent stake in BofA in the first quarter after converting its Merrill shares into BofA in January. Temasek has not said how much it lost in the process, but Reuters estimated the loss was more than $3 billion.

Temasek announced in February that Ho will step down and be replaced by Chip Goodyear, the former CEO of BHP Billiton , on October 1.

Our investment thesis had changed from Merrill's specific businesses to the more diversified BoA linkage to the broader U.S. economy. The risk-return environment had also changed substantially, Myrna Thomas, managing director for corporate affairs, said in the letter.

Temasek's aim is to ensure that its portfolio delivers returns that are higher than the cost of capital employed on a risk-adjusted basis, Thomas said.

We may choose to divest an investment, even at a loss, to optimize our risk or portfolio exposure, or if there are better opportunities elsewhere or later, she added.

Temasek, which like other sovereign wealth funds, plowed billions into Merrill Lynch in the early phase of the credit crisis, saw the value of its portfolio plunge 31 percent to S$127 billion between March 31 and Nov 30 last year during the severe market turmoil.

KEY QUESTION UNANSWERED

Financial investments accounted for 40 percent of its portfolio.

The letter doesn't give the answer that everybody is asking. How much did they lose?, Leong Sze Hian, president of the Society of Financial Services Professionals, told Reuters.

The exact losses are difficult to quantify because Temasek had also offloaded about 30 million Merrill shares last year in smaller lots, reducing its exposure to the investment bank by the time BofA took over Merrill.

Conraj Raj, editor-at-large at the Today newspaper in Singapore, threw the spotlight on the sovereign wealth fund's stated strategy of taking a long-term view of its investments.

After all, it has been drummed into us ad nauseam that both Temasek and its cousin, the Government of Singapore Investment Corporation, invest for the long term with a time horizon that could stretch for as long as 50 years, he wrote on May 18.

Whatever happened to the sovereign wealth fund's (SWF) strategy of taking a long-term view of its investments?

Singapore's bigger sovereign wealth fund, GIC, on the other hand said it was a long-term investor in Citigroup and UBS .

It is difficult to understand why a long-term investor like Temasek was willing to stick with a dud like Australia's ABC Learning centers to the end, but did not try to exercise a little bit more patience with a U.S. government-backed entity like BofA, Png Eng Huat wrote in a letter to Straits Times forum.

The U.S. government has stated clearly that it will not nationalize BofA even though it is technically the largest shareholder of the bank.

(Editing by Muralikumar Anantharaman)

Investment Merrill Lynch Bank of america