The move has been taken following research by the group, which found that the majority of small and medium-sized businesses in the capital are ill-prepared for a terrorist attack.
London First staff are now in talks with the police and security services group the National Counter Terrorist Security Office on the details of advice to be given.
The campaign was planned for a launch at some point this year, but has been brought forward due to the war in Iraq and the heightened risk of an attack.
According to Andrew Marre, the former ITV Digital and Department for Culture, Media and Sport PR head who joined London First last month as communications director, the campaign will be PR and direct mail driven.
Marre said: 'The situation at the moment has brought a sense of urgency.
To many, particularly smaller businesses, not a lot of thought has gone into the possibility of a terrorist attack.'
He added advice will also be given to larger firms, many of whom have addressed the issue of an attack but have yet to test their emergency plans.
Advice likely to be offered will include ensuring firms have up-to-date records of staff's families in the event of an attack.
'If there is damage to a building, are there duplicate sets of records?
These are things firms need to think about,' Marre said.
It is understood that CD-ROMS will also be distributed to businesses as part of the campaign, which will be handled in-house by London First's three-strong team.
Other campaigns by the body, which was set up in the early 1990s, this year include a stepping up of its lobbying of the GLA surrounding Mayor Ken Livingstone's Draft London Plan.