The average fraud case involves the analysis of 500,000 emails and electronic documents, according to a newly published report by PricewaterhouseCoopers (PwC).

Computer records now make up over 80 per cent of the evidence in fraud cases, and digital fraud investigations have tripled in the past two years.

The consulting firm has investigated 150 cases in the past 14 months, and said that the number of cases reaching the crown courts is at the highest level for two years.

PwC also found that such cases are becoming increasingly complex. A recent multinational investigation involved 90 computers in 18 countries and the analysis of 2.6 million email messages.

In another case a fraud focused on a single inbox containing 450,000 emails.

Such cases also have a geographic bias, with 80 per cent of cases centring on London and the south east.

Fraud cases involving identity theft showed a marked increase over the past two years.