Major changes at the top of Ford Motor Company - including reorganisation of its Premier Automotive Group - this week created waves of concern and speculation about the futures of top executives.

Jac Nasser's sacking as chief executive had been brewing for months but managing director Jonathan Browning's decision to leave Jaguar shocked manufacturing and retailing bosses.

Carlos Ghosn, the Renault group executive turning round the affiliated Nissan, is being tipped to move to Ford. Chairman Bill Clay Ford wants more direct control and has former Jaguar chairman and Ford of Europe president Sir Nick Scheele as his chief operating officer. This is widely viewed in Detroit as a holding operation.

Meanwhile, Ford's Premier Automotive Group is to have a joint operating committee to find ways for British subsidiaries Jaguar, Land Rover and Aston Martin to share major components.

Mr Browning resigned after Land Rover chairman and chief executive Bob Dover was chosen to head the PAG taskforce. Mr Dover's training as an engineer made him the logical choice but the exclusion of Volvo and Lincoln raises questions about the future of PAG.

Now Mr Browning is seen as a possible chief executive of BMW's Rolls-Royce. A plant under construction at Goodwood, West Sussex, will build cars from 2003.

Garel Rhys, automotive professor at Cardiff University Business School, said: "Jonathan Browning was committed to Jaguar succeeding and wondered how the company could stand alone as part of the JOC at PAG.

"Ford knows it needs a manufacturing critical mass - even 600,000 Jaguars and Land Rovers a year leaves it well behind BMW.

"Production economy at PAG will be a difficult trick to pull off - it's a high-wire act. Ford needs Jaguar's higher margins but some will worry the JOC is the first step back to the old BL Vehicles, when Jaguar was in the same manufacturing group as Austin."

Prof Rhys said Jaguar, which had solved quality problems, could help Land Rover, "still miles away from doing it". A pointer to PAG ambitions to move the brands closer comes with the new Range Rover which Mr Dover described as "the most capable vehicle in the world". He added: "We wanted to set it apart from all off-road competitors and offer an interior that beats luxury saloon rivals."

A Jaguar dealer said: "There is a logic in PAG brands sharing components but you don't need a joint operation. "I'm fearful of a Jaguar door handle being used on another brand as a way of saving money."