Barclays swung into the red during 2017, posting a loss of £1.9bn.
This compared to a £1.6bn profit for the previous year but the bank said it had been hit by a one-off tax charge of £901m as a result of tax reforms in the US.
The banking giant said it was also hit by losses of £2.5m related to the sale of Barclays Africa Group Ltd.
But once these costs are excluded, Barclays saw its profits before tax increase by 10 per cent to £3.5bn.
Revenues fell by 2 per cent to £21bn while its expenses also fell by 5 per cent to £15bn.
Jes Staley, chief executive of Barclays, said: "2017 was a year of considerable strategic progress for Barclays
"We have a portfolio of profitable businesses, producing significant earnings, and have plans and investments in place to grow those earnings over time.
"While we still have a number of legacy conduct issues to address, I am confident in the capacity of this business to generate excess capital going forward, and it remains our intention over time to return a greater proportion of that excess capital to shareholders through dividends, and other means of capital distribution, including share buybacks."
The Financial Conduct Authority has been investigating Mr Staley after he tried to identify a whistleblower within the company who criticised a senior employee.
Barclays also paid out £1.2bn during 2017 for litigation and conduct issues, including £700m for payment protection insurance.
The bank's net interest income was up by 1 per cent to £6bn while its net interest margin - the difference between the interest generated from mortgages to that paid out on deposits - fell to 3.49 per cent.
Barclays said its growth in net interest income was in part due to growth in loans and advances to customers and deposits, partially offset by the impact of the UK base rate reduction in 2016.
With regards to mortgages, the bank made gross loans and advances of £132bn during 2017, up from £129bn the previous year.