By Edward Taylor

FRANKFURT (Reuters) - Deutsche Bank plunged to a 2.6-billion-euro ($3.5 billion) quarterly loss after it took charges aimed at drawing a line under a series of scandals and cleaning up its balance sheet without asking shareholders for cash.

Germany's biggest lender said on Thursday the pretax loss was partly due to a 1-billion-euro hit to cover legal risks, including its potential exposure to an industry-wide scandal involving the fixing of benchmark interest rates.

It also announced a 1.9-billion-euro impairment charge on underperforming assets, shifting them to a "non-core" division for potential run down or sale as part of a move to strengthen its capital position and avoid a rights issue.

"We have been very consistent. We have said we do not believe it is in our shareholders' best interests. We have shown that we are willing to take pain," Co-Chief Executive Anshu Jain told a conference call when asked about a possible rights issue.

"This said, clearly, it is a very uncertain world. There is a plan B. We will not rule out any option that is in the best interest of Deutsche Bank."

Banks across the world are slashing costs and selling or writing off weaker assets in a bid to meet tougher capital rules aimed at preventing a repeat of the 2008 financial crisis.

Deutsche Bank has cut its risk-weighted asset (RWA) base, helping to raise its core tier one capital ratio under Basel III rules to 8 percent at the end of 2012 from under 6 percent at the end of 2011. RWAs are a bank's assets, usually loans, adjusted for the likelihood of non-payment.

However, Deutsche Bank's ratio is still among the lowest for a major European bank and some analysts said its capital cushion could drop if global regulators harmonize the way banks estimate the riskiness of their loan books.

"They might apply some minimum floor for RWAs, which would cost Deutsche Bank a lot ... Their internal models could have to be thrown out the window," said Espirito Santo analyst Andrew Lim, who has a "sell" recommendation on Deutsche Bank shares.

Lim believes the bank needs between 15 billion and 20 billion euros of additional capital.

"I think they need that amount ... they might not be made to raise it, they haven't been made to raise it by (German regulator) BaFin. The ECB might take a much more stern stance and force them to raise equity or reduce their balance sheet," he added, referring to the European Central Bank which is taking on supervision of banks across the region.

Deutsche Bank shares were up 0.7 percent to 37.39 euros at 7 a.m. ET. The stock has lagged rivals over the past 12 months, rising 15 percent compared with a 21 percent increase for the benchmark Stoxx Europe 600 Banks Index.

LEGAL LIABILITIES

Deutsche Bank said it was too early to say if allegations its staff were involved in rigging the London Inter Bank Offered Rate (Libor) would be settled this year.

Switzerland's UBS and Britain's Barclays paid a total of nearly $2 billion to settle such allegations.

Deutsche Bank Chief Financial Officer Stefan Krause played down the legal problems, saying peers had similar issues. "The tail of legal liabilities is fairly typical," he told analysts. "The regulatory and litigation environment remains challenging."

The bank said its new "non-core" division would house 125 billion euros worth of assets that either eat up too much capital or fail to throw off sufficient profits.

The bulk of the impairment charge on these assets - 1.2 billion euros - was attributable to the bank's corporate banking and securities unit (CB&S), its main investment banking arm and traditionally its strongest performer.

CB&S posted a quarterly pretax loss of 548 million euros.

Analysts had expected Deutsche Bank to report a fourth-quarter pretax profit of 116 million euros, the average of seven estimates in a Reuters poll of banks and brokerages showed. It was not immediately clear whether the analyst estimates had factored in goodwill impairments.

The bank's net loss for the quarter was 2.2 billion euros.

Since the end of 2011, the bank has reduced headcount by 2,777, the results showed. it is in the midst of a restructuring drive designed to achieve annual cost savings of 4.5 billion euros by 2015.

(Reporting by Edward Taylor Arno Schuetze and Jonathan Gould; Writing by Carmel Crimmins; Editing by Victoria Bryan and Mark Potter)

(This story was refiled to correct the spelling of 'tail' in the fifteenth paragraph, from 'tale'.)