Royal Dutch Shell has issued a shock profit warning, with the company's new boss Ben van Beurden admitting that the oil giant's performance was "not what I expect" from the group in 2013.

Mr Van Beurden - who succeeded Peter Voser as chief executive on 1 January - said the firm's fourth quarter figures were expected to be "significantly lower than recent levels of profitability".

Its fourth quarter underlying earnings are now expected to almost halve to around $2.9 billion.

This is set to leave full year results 23% lower at $19.5 billion.

Mr Van Beurden said: "Our 2013 performance was not what I expect from Shell."

Shares fell 4% after the profit alert, which comes after an already disappointing past few months for the Anglo-Dutch group.

Former chief Mr Voser warned in October that Shell was "entering into a divestment phase" as he reported a worse than expected slump in third-quarter profits.

It marks a gloomy start to Mr Van Beurden's tenure at the group.

The Dutch national had risen through the ranks over three decades before securing the top post, beating off competition from internal and external candidates.

He joined the Shell group of companies in 1983 and has held a number of technical and commercial roles in both the upstream and downstream businesses, including in London.

His predecessor Mr Voser, who had been chief executive of Shell since July 2009, announced plans to retire from the role in May to pursue a "lifestyle change", telling staff he wanted to spend more time with his family.