Another day, another lawsuit for Goldman Sachs.

Yesterday, the US regulator of credit unions sued the gold-plated investment bank run by Chief Executive Lloyd Blankfein, accusing it of selling $1.2 billion in dicey mortgage-backed securities to two credit unions that later failed.

The suit, filed in Los Angeles federal court by the National Credit Union Administration, seeks nearly $500 million in damages.

Goldman sold the credit unions “questionable securities” and “misrepresented” the risks associated with the risk-laden assets, according to the suit.

Goldman declined to comment.

The action is part of a flurry of suits filed by the regulator against Wall Street banks, including JPMorgan Chase and Royal Bank of Scotland, in a bid to recover about $50 billion in losses.

It comes as signs have emerged that the world’s most profitable investment bank may be losing its white-hot sheen on The Street.

Goldman reported one of its worst trading results — that it lost money in nearly 25 percent of the trading days in the second quarter. Shares rose 4.3 percent to $122.73, after hitting a 52-week low on Monday.