'Hostile intelligence agencies' made hundreds of attempts to hack into the Treasury's computer system last year, Chancellor George Osborne has revealed.
Osborne said that the number of attempts averaged at least one attack a day.
"During 2010, hostile intelligence agencies made hundreds of serious and pre-planned attempts to break into the Treasury's computer system. It averaged out as more than one attempt per day.
"This makes the Treasury one of the most targeted departments across Whitehall," Osborne told delegates at the Google Zeitgeist conference in Hertfordshire.
He said that more than 20,000 malicious emails are sent to government networks "in any given month".
He described one incident to delegates: "At some point last year, a perfectly legitimate G20-related email was sent to HM Treasury and some other international partners. Within minutes, it appeared that the email had been re-sent to the same distribution list.
"In fact, in the second email the legitimate attachment had been swapped for a file containing malicious code. Fortunately, our systems identified this attack and stopped it."
Osborne was using his keynote address at the Google conference to describe how the internet age is changing how the government operates, and announced a number of new initiatives and staff appointments.
He said that the government has just recruited Beth Noveck, the deputy chief technical officer who ran President Obama's Open Government Initiative, to lead the government's work on making policy-making more open and transparent in the internet age.
Noveck will work alongside the UK Digital Champion Martha Lane Fox "to harness new technologies to make government more innovative and accountable", Osborne explained.
In terms of new initiatives, Osborne revealed that Imperial College London and University College London are developing plans to create a new research centre together to develop new technologies to make use of the large amount of data being generated in cities, such as transport data and energy data.
The 'smart cities' research centre will be based in the UK's 'Silicon Roundabout', Tech City in Shoreditch, East London.
Meanwhile, Osborne said that the government has been working with technology companies to design programmes aimed at developing the future generation of IT workers.
For example, BlackBerry will launch an competition for UK schools, to teach them how to design new online applications, and Intel is running a range of schemes to help young people set up their own online businesses.
In addition, YouGov is sponsoring a StartUp Summer programme to provide mentoring, research, funding and cash prizes to encourage university students to become internet entrepreneurs.
"These schemes will benefit thousands of young people in the years ahead," said Osborne.