PRWeek can reveal that the two agencies are finalising a deal that could see Foresight merged into the Lansons brand in a matter of weeks.
As a prelude to the deal being inked, Foresight moved out of its Westminster premises last week and is now based at Lansons' head office in Farringdon, east London.
Lansons chief executive Tony Langham confirmed the deal was close to completion.
He said: 'We're committed to becoming a major player in the public policy space. I'm impressed by Mark Adams and the business he has built. We look forward to completing the deal and working with him in future.'
Foresight was founded in 2001 by Adams, a former civil servant who was private secretary to both John Major and Tony Blair during their time as prime ministers.
The agency has three full-time and three part-time staff. Key retained clients include the Police Federation and Conserve the Chilterns and Countryside, the campaign to protect the Chiltern Hills and countryside from the proposed High Speed 2 (HS2) rail link between London and Birmingham.
Lansons merged its public affairs and regulatory consulting arms earlier this year. The resulting eight-strong practice has annual fees of about £750,000. Senior figures in the practice are board director Ralph Jackson and head of public affairs Ben Abbotts.