Mick Deats, deputy head of the unit, said the complex, time-consuming nature of investigations meant the unit could not investigate every case reported.
Deats, responding to demands from business groups for greater funding for high-tech crime, as reported in last week's Computer Weekly, said more resources were needed.
"We see from our research that there is an increase in high-tech crime. We could do with more resources to deal with it. The more we can win the confidence of industry, the better," he said.
"These are complex, expensive investigations. We have just finished a trial at the Old Bailey that took six months and much longer to investigate. We cannot take on as many cases as we want."
The increased use of computers and high-tech equipment such as mobile phone cameras meant that local high-tech police units were wrestling with a huge workload, said Deats.
"The forces are struggling under the amount of digital evidence. If there is an investigation into a murder or an assault, there might be a digital picture on a mobile phone. CCTV might need to be examined. Digital evidence is the responsibility of the local high-tech crime unit," he said.
Deats called for tougher sentences for computer criminals, and for a greater understanding by the courts of the damage that e-crime causes businesses. Although the Computer Misuse Act allows sentences of up to five years for serious offences, they are rarely applied by the courts.
The law needs to be updated to give more legal protection against denial of service attacks and theft of company data, he said.