RNS's share of financial company announcements fell to 88.5 per cent this week, putting out 7,804 announcements.
While the LSE-owned service remains the leader in the market, United Business Media's PR Newswire is gaining ground, notching up 824 announcements, or 9.3 per cent.
PR Newswire has reportedly signed non-exclusive deals with Brunswick, Tavistock Communications, The Maitland Consultancy and Financial Dynamics.
Other corporate clients include Logica, Cable & Wireless, BAA, Somerfield and Cadbury.
Rival regulatory information services only managed to bag just over two per cent between them.