The talks follow an approach made by UBM chief executive David Levin to Peter Rigby, Informa's executive chairman. Following press speculation, Informa confirmed in a statement it was discussing an "all-share merger".
Informa, which owns market research company Datamonitor, has been seen as vulnerable to bid approaches for a number of months, with concerns about its £1.1bn of debt.
UBM, which publishes business title Property Week, as well as running one of the world's largest exhibitions units, has been acquisitive in recent years and earns significant revenues from its international operations.
A merger between the two companies would make it eligible for the FTSE 100 index.