Standard & Poor's Rating Services has cut the Indian carmaker's corporate credit rating from BB+ to BB and said the company remained on “negative watch”.

S&P said the rating action reflected Tata's heightened financial leverage, resulting from the $3bn (£1.5m) bridge loan that has been taken out to fund the acquisition.

The ratings services firm also attributed the move to a more challenging business environment for the company's domestic passenger and commercial vehicle segments in India and for the high-end luxury car segments.

Tata's shares have fallen 23 per cent since it became the frontrunner in the race for the Ford marques in January.

Investors have expressed concern about the additional debt and challenges faced by Tata to manage the two brands.