Cyber security experts from industry are to operate alongside the intelligence agencies for the first time.
The government is establishing a new "fusion cell" where analysts from MI5 and GCHQ will work side-by-side with private sector counterparts.
The cell is part of the Cyber Security Information Sharing Partnership (CISP), launched this week, intended to provide industry with a forum to disseminate details of techniques used by online attackers as well as methods of countering them.
At any one time there will be around 12 to 15 analysts working at the cell, based at an undisclosed location in London.
"What the fusion cell will be doing is pulling together a single, richer intelligence picture of what is going on in cyberspace and the threats attacking the UK," one senior official said.
"What we are trying to do is get that better intelligence picture and push it out to industry in a way that they can take action on, so it is very action-orientated."
Although the industry representatives will not have direct access to classified intelligence material, they will have to undergo security vetting.
The CISP initiative grew out of talks in 2011 between industry and Prime Minister David Cameron. It led to a pilot project last year involving 80 leading companies, codenamed Programme Auburn.
It will be established on a permanent footing and expanded to cover 160 firms from the finance, defence, energy, telecoms and pharmaceutical sectors.
With firms deeply reluctant to discuss cyber attacks or breaches of security in public, officials acknowledge that confidentiality is crucial, so companies involved will not be named.
"Everything about information-sharing has to be based on trust," one official said. "Most companies still remain cautious about talking about the cyber threats they face in public."
Firms involved will also have access to a secure web portal - described as a "Facebook for cyber security threats" - run on social network lines, where they can choose who they share information with.
It is expected that other firms will be invited to join as the scheme develops, although officials stressed that future expansion would have to be at a pace consistent with maintaining trust and confidentiality.
Launching the scheme, Cabinet Office Minister Francis Maude said the government was determined to make Britain one of the safest places to do business in cyberspace.
"We know that cyber attacks are happening on an industrial scale and businesses are by far the biggest victims of cyber crime in terms of industrial espionage and intellectual property theft with losses to the UK economy running into the billions of pounds annually," he said.
"This innovative partnership is breaking new ground through a truly collaborative partnership for sharing information on threats and to protect UK interests in cyberspace."