Loewy, which bought the two agencies in 2007 and 2006 respectively, would only confirm it was considering this option. But industry sources predicted the agencies would be merged into the Loewy brand in a matter of weeks.
The development comes soon after Loewy founder and CEO Charlie Hoult was moved to the role of vice-president (development) and replaced by Iain Johnston, who was appointed as interim group CEO in May.
Johnston did not deny that merging some of its PR agencies into the wider brand was under discussion. 'When you're running a business of 400 people, you're constantly developing plans for accelerating growth,' he said.
But he insisted: 'We haven't made any decisions yet. One option is integration. I think the key is we're looking at how our business will be strongest for growth.'
Johnston said the agency was considering, among other things, how it would be physically possible to merge the three companies, which are based in different places.
Johnston's remit is 'to take the business into its next phase'. He said the search for a new CEO was ongoing.
In February, Lexis founder Bill Jones was hired by Loewy to chair its five PR agencies - BMA, Mantra, Rainier and sister agencies Custard PR and Lighthouse. He said his role was to 'streamline the reporting process'. Mantra founding partner Debbie Wosskow left the agency at the end of February, just seven months after selling up to Loewy.
The Rainier deal is thought to be worth £5m over three years, while Mantra is believed to have been sold by Wosskow and Lawrence Dore at a slightly higher price.