But, on Friday, the all-party Commons transport committee said it was "astounded" by the hold-up of the EIB loan.

It will help Jaguar develop "clean cars" but must first be guaranteed by Whitehall.

Hitting back at the committee's accusations of needless delay, Lord Mandelson said it would "not be too long" before a deal was agreed, but added: "I first started talking to Jaguar Land Rover in November last year.

"It took until March for their plan to be assembled and then a further, quite lengthy, period for them to be specific, to pin down exactly what they were asking for from the British government.

"But they know we are standing behind them and, when the time comes, we will be able to help put in place the financial assistance they need."

The Business Secretary gave no further clues to explain the hold-up, other than to say any assistance to Jaguar must be part of a "wider longer-term plan" for its future.

The 300 Halewood job losses were announced on Wednesday last week when plant bosses confirmed the Baby Jag would cease production at the end of the year.

The popular Freelander 4x4 model is still produced at the factory, with the possibility of a future seven-seater version.

But the big hope for the Knowsley plant rests on the concept LRX car, a “Baby Land Rover” which will achieve an environmentally-friendly 60 miles per gallon.

Government funding of £27m has been offered and a chunk of the £340m loan is earmarked for the LRX.