Oil company revenues from Africa and the Middle East declined by $15.2bn in 2013, according to financial services company EY.

Income was $136.4bn in 2013, down from $151.6bn in 2012, according the firm’s new report.

Although revenues were down in 2013, capital expenditure was higher. Oil companies spent $45.4bn in 2013 compared with $42.8bn in 2012, with development of oil assets seeing the biggest increase in spending.

Oil companies are likely to face further declines over 2014 due to the slump in oil prices.

Brent crude has lost more than 40 per cent over the year.

During 2013, average production costs in Africa and the Middle East for a single barrel of oil was $13.19, lower than any other region, according to the EY report.

This compares with $24.28 in the Asia-Pacific, $20.64 in Canada, $17.45 in Europe and $14.68 in the US. The worldwide average was $18.94.