Deutsche Bank, Germany's biggest bank, said that bottom-line profits were up sharply in the whole of 2011, even though after-tax earnings dropped in the fourth quarter.

Deutsche Bank said in a statement on Thursday it booked net profit of 4.3 billion euros ($5.7 billion) last year, up from 2.3 billion euros a year earlier.

Nevertheless, bottom-line earnings declined sharply in the last three months of 2011, totalling only 186 million euros, compared with 605 million euros in the same period a year earlier.

"Once again, Deutsche Bank has proved its ability to deliver substantial earnings in challenging conditions," said chief executive Josef Ackermann.

"In 2011, our classic banking business produced record earnings, thus counterbalancing the impact of weak markets in investmment banking. We also significantly strengthened our capital base, boosted our liquidity reserves and reinforced our funding position," said the Swiss-born chief executive, who is scheduled to step down in May after 10 years at the helm.