This morning, Sir Frank announced he was setting up a new advertising agency based in London with a number of as-yet-unnamed partners.
The Lowe founder announced at 10.30am that he was setting up with a number of as-yet-undisclosed partners.
It is understood the start-up will have other business besides Tesco with which to launch.
By late morning Garry Lace, the Lowe chief executive, had announced to staff that Weinberger, who has overseen the Tesco creative work for many years, was quitting.
The supermarket giant has yet to make its intentions known but sources say it is almost inevitable that the account will move.
The move by Sir Frank comes three months after the ending of restrictive covenants imposed on him by the Lowe agency's Interpublic parent, which prevented him poaching Lowe London's clients or staff.
The loss of Tesco would be a devastating blow for Lowe, which has been attempting to get back on course after a series of big account losses over the past two years.
Questions remain, however, about the new agency's capacity to handle such a labour-intensive account as Tesco, for which Lowe produces 1,900 print and TV ads each year.
Weinberger has been a long-time critic of the way in which Frank Lowe was ousted from the agency. In February, he offered and then withdrew his resignation as chairman in protest at Lace's appointment as chief executive.
Lowe, a legend in advertising circles and one of the founders of Lowe Howard-Spink, has long been rumoured to be making a return to the advertising industry.
Most recently, it was reported that Lowe was interested in buying back the agency that bears his name from troubled parent company, Interpublic Group. Prior to that, speculation had it that he may form a start up with former colleagues and attempt to take the Tesco account from Lowe London.
Sir Frank Lowe exited the agency world in 2003 when he retired from Lowe 22 years after he founded it. He had started out in the postroom of J Walter Thompson in 1960, and earned a reputation as one of the great creative talents in the industry.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the Forum.