Workers' leaders at Jaguar and Land Rover have lent their support to Tata's bid for the two carmakers.
The decision followed presentations to the shop stewards and the leadership of Unite by private equity firm One Equity Partners, and Indian industrial groups Tata and Mahindra and Mahindra.
Tony Woodley, Unite joint general secretary, said the union's shop stew-ards at Jaguar and Land Rover had made clear their preference to stay as part of Ford, which has put up for sale the two car makers employing 15,000 people in the Midlands.
But if a sale was decided, the union representatives felt the best interests of the workforce would be served by finding a partner with an established presence and background in manufacturing.
Tata has been praised for its stew-ardship of Corus, which it bought in January for £5.75 billion.
A spokesman for Unite said: "Mr Woodley said the stewards had made their decision based on the reports from the presentations made by all the shortlisted bidders from the union representatives who attended.
"Based on serving the best interests of the union members at Jaguar Land Rover, the stewards agreed that Tata best fit these criteria."
The union said it could not expand on these reasons because it was bound by a confidentiality clause as part of its negotiations with Ford.
The American carmaker said it wants to complete the sale of Jaguar and Land Rover by either the end of this year or the beginning of 2008.
Meanwhile Business Secretary John Hutton has warned that thousands of UK jobs in the Jaguar and Land Rover supply chain could be at risk with the proposed sale of the marques.
He told the Commons Business Committee the Government was confident the successful bidders for the car-makers would keep production in the UK.
But Mr Hutton refused to give any similar assurance about the brands' supply chains.
