Profits at Barclays fell by 21% in the first half of the year as the bank set aside a further £400m to compensate customers mis-sold payment protection insurance (PPI).
Profits for the six months to 30 June fell from £2.6bn last year to £2bn.
The new charge for PPI means the mis-selling scandal has so far cost Barclays a total of £7.8bn.
Profits were depressed by a £1.9bn loss on parts of the business that the bank has ear-marked for sale.
This includes its French retail, wealth and investment management businesses which it is in talks to sell to private equity firm, AnaCap Financial Partners.
Commenting on the impact of Britain's vote to leave the European Union, Jes Staley, who became chief executive last year, said he had no plans to alter the bank's strategy of selling parts of the business and strengthening its retail and investment banking operations.
He said: "We remain confident that it is the right plan for Barclays, and see no reason to adjust it, or the pace of delivery, in light of the vote by the UK last month to exit the EU."
However, the bank set out a number of risks it now faces, which include possible changes to "passporting" rights that allows the bank to operate across the EU.
It also it faces uncertainty over whether there will be any changes to freedom of employee movement, which would "impact Barclays' access to the EU talent pool" as well as "decisions on hiring from the EU of critical roles".
Analysis: Dominic O'Connell, BBC Today business presenter
While Jes Staley did not make the blunt Brexit warning made yesterday by his opposite number of Lloyds Banking Group, Antonio Horta Orsorio, the fine print of the Barclays statement makes plain its concerns.
It says the referendum result means "the long-term nature of the UK's relationship with the EU is unclear… in the interim, there is a risk of uncertainty for both the UK and the EU, which could adversely affect the economy of the UK and the other economies in which we operate".
It also lays out the detailed risks to its UK business, including the threat to "passporting" rights, which allow banks and other financial services companies to sell their services across the EU, and the threat to hiring staff from the possible end to the free movement of people.
'Jekyll and Hyde'
David Cheetham, market analyst at XTB.com, said: "Not only does the decision by Britons to exit the EU cloud the business environment for the foreseeable future with a heightened level of uncertainty, the likely response from the Bank of England in further easing monetary policy will provide an additional headwind to all banks as operating margins are squeezed further."
Shares in Barclays rose by 4.1% in early trading to 152.4p after the bank revealed an improvement from its investment bank arm in the second quarter after it reported disappointing results in the first three months of its financial year
Analysts also pointed to an improvement in Barclays' main businesses in retail and investment banking where profit in the first half rose by 19% to £3.9bn. This include the £615m Barclays made on selling its share in Visa Europe Limited.
Laith Khalaf, senior analyst at Hargreaves Lansdown, said: "Barclays is a bit of a Jekyll and Hyde character at the moment, but Doctor Jekyll is starting to gain more control, as all the grisly bits of the bank get wound down."
He added: "The new boss, Jes Staley, seems determined to get on with the task of getting rid of the bad bank sooner rather than later.
"If and when Barclays gets rid of its non-core businesses it should start to look more like an upstanding citizen of the banking sector, but that is still going to take until 2017 at least, a decade after the banking crisis kicked off."