The developers said they had not been notified by Farrell of his intention to pull out of the scheme.
But the Ham & High, a north London weekly newspaper, reported in this week's edition that Farrell had issued a statement in which he suggested that there was "a fresh possibility of some involvement with the project".
Council officers are known to have been contacting Farrell in an effort to persuade his practice to return.
One officer conceded that the loss of a "name" architect would be a blow.
The squabble is the latest blow for the leisure centre and housing scheme, which was already delayed for a year while developers fought off a legal challenge from local groups.
As part of the scheme John McAslan + Partners has been appointed architect on a £3m library refurbishment and Bennetts Associates is heading a £9.86m theatre project.