The new set-up would see a small number of Conservative and Liberal Democrat media strategists sitting side-by-side.
Lib Dem insiders said the party's director of general election communications Jonny Oates would occupy a key role in the unit.
In the new PR operation, Oates is expected to work closely with Andy Coulson, the former Conservative Party communications chief who is in line for the Downing Street communications director role.
Other Lib Dem communications staff are expected to be based in the Cabinet Office, working directly for deputy prime minister Nick Clegg.
The new Downing Street communications unit is expected to get the green light next week. Well-placed sources told PRWeek it would help the coalition government to successfully integrate announcements and to avoid mixed messages.
