Barclays has posted a 5% fall in profits for the first three months of the year as earnings from its investment bank slumped by half.
Adjusted pre-tax profits fell to £1.69 billion after the bank warned last month that it would be hit by the performance of the division.
The investment bank, which faces a shake-up likely to costs hundreds of jobs when Barclays announces a strategy review on Thursday, saw pre-tax profits fall by 49% to £668 million.
It was driven by a "significant decline" of 41% in income from its fixed income, credit and commodities business as well as changes to the business.
Barclays chairman Sir David Walker has hinted at a shrinking of the investment banking arm following a controversial rise in its bonus pool last year despite declining profits at the group.
It has been reported that the group is to create a "bad bank" or non-core unit as it seeks to exit parts of its fixed-income business and loss-making European branch network.
Chief executive Antony Jenkins said the first quarter had seen strong performance from its retail, cards and business banking arms, while a programme of cost reduction had driven underlying operating expenses to the lowest level since 2009.
He said this week's review "will address issues underlying the performance challenges we have recently experienced, including positioning the investment bank for the new operating and regulatory environment".
The group said it remained "cautious about the trading environment" adding: "We remain focused on structurally reducing the cost base in order to improve returns."
Barclays said pre-tax profits at its UK retail and business banking arm rose 20% to £360 million primarily driven by income growth and lower impairment charges.
Earlier this year, Barclays announced a 32% fall in annual profits to £5.2 billion and confirmed plans to cut up to 12,000 jobs this year. But the bonus pool was raised 10% to £2.38 billion.