Commincations intelligence agency GCHQ said in the Times that sensitive data on Government computers has been targeted, as well as defence, technology and engineering firms' designs.
There was also a 'significant' but ultimately unsuccessful internet-based attack on Foreign Office computers in the summer.
GCHQ's Iain Lobban said that he found the volume of attacks disturbing.
He went on: "I can attest to attempts to steal British ideas and designs - in the IT, technology, defence, engineering and energy sectors, as well as other industries - to gain commercial advantage or to profit from secret knowledge of contractual arrangements.
"Such intellectual property theft doesn't just cost the companies concerned; it represents an attack on the UK's continued economic wellbeing."
Tomorrow the Government will be holding a two-day event- the London Conference on Cyberspace, hosted by foreign secretary William Hague - which aims to bring together key figures from government and industry, alongside security experts (including representatives from Microsoft and Kaspersky), in order to better tackle cyber-issues.
It will concentrate on five themes: economic growth and development; social benefits; cyber crime; safe and reliable access; international security.