Fitch Ratings in New York said today that troubled bond insurer Ambac Financial Group Inc. has asked Fitch to withdraw all ratings of Ambac and subsidiaries. Fitch said it is considering the request.

Fitch last took action on the insurer March 12 when it affirmed Ambac's financial strength rating at "double-A" with a negative outlook.

The affirmations came after Ambac completed raising $1.5 billion of new equity capital, which the firm did after its January announcement that subprime-related risks had led to a fourth-quarter 2007 net loss of $3.26 billion, or a net loss of $31.85 on a per share basis.

Fitch said in March that Ambac claims paying resources fell below Fitch's "triple-A" capital targets by a range of $4-to-$5 billion.

Ambac officials could not immediately be reached for comment. Earlier this month, after Moody's threatened to downgrade the firm, Doug Renfield-Miller, executive vice president for Ambac, said during an investor's conference, "We have strong liquidity and capabilities."

He said that from a capital standpoint, the company is $500 million above loss targets set by Moody's and $700 million above Standard & Poor's. The problem lies on the reliance on models that optimize stress losses used by the rating firms, he said.

"We believe from a capital liquidity standpoint we are 'triple-A,'" Mr. Renfield-Miller said.

He said the company made mistakes, taking on risks in collateralized debt obligations it should not have, and has learned from that.

He added that most of the CDOs were sold off. He said the losses from those deals have had an "outsized impact" on the perception of the company, but the carrier is generating good earnings despite the fact it is not writing much new business--something that Moody's threat of downgrade will not help.