By Jorn Madslien BBC News Online business reporter at the Paris Motor Show

It's not a question of threat, it's a reality Carlos Ghosn, president and chief executive, Nissan Motor

In an interview with BBC News Online, Mr Ghosn made it clear that the plant's future would depend on whether the UK adopted the euro.

"We are worried about having our cost base in pounds and to have our revenue base in euros," he said.

"This is a situation we don't like.

"We had this situation when we decided to make the investments on the Micra."

"We ended up deciding to make the Micra in Sunderland," Mr Ghosn added, referring to the company's �235m ($369m) investment in January last year to build the model in the north of England.

"When the next investments come in the next couple of years, we hope we don't have to go through the same kind of analysis," Mr Ghosn said in a thinly veiled call for UK membership of the euro.

"Obviously, that is not our decision. It's the decision of the UK government.

"That's why it's our duty to express our difficulties and our hopes and let them make the decisions."

Nissan presented the new Micra for the first time at the Paris Motor Show a week ago.

Reality

When asked whether he was threatening to shift production abroad unless the UK joined the euro, Mr Ghosn responded:

Nissan's Sunderland factory: Europe's most efficient

"No, it's a reality. It's not a question of threat, it's a reality that we will take this into consideration each time we have to make an investment."

"We would like, as much as possible, to have Sunderland producing a lot of cars, but at the same time making cars that would allow us to make a profit."

This would be easier if Nissan's exchange-rate risks could be minimised or eliminated.

But Mr Ghosn declined to say whether he thought this could be achieved without the UK joining the euro.

"We don't discuss how [this] should be achieved, we discuss our objective," he said.

Competitive advantage

Two years ago, Nissan decided to produce the Micra in Sunderland rather than in France where both its costs and its revenues would be in euros.

Mr Ghosn: Soon to be in charge of Renault too

In a close decision, Sunderland was chosen because it was, and still is, Europe's most efficient car manufacturing plant.

"So the only concern we have in Sunderland is not about the plant but about this [exchange-rate] environment," Mr Ghosn said.

After all, the Micra - 1.3 million of which have been sold in the last decade - is crucial to Nissan's future in Europe.

"The Micra is a very important car for us," Mr Ghosn said.

"It's going to represent practically one third of all our sales in Europe."

No compromise

Nissan wants the new Micra to return profits almost immediately, Mr Ghosn said.

I said immediately that I would be keeping my job as president and chief executive of Nissan and at the same time become president and chief executive of Renault Carlos Ghosn

"If we thought that it would be very difficult to make money out of the Micra in Europe, frankly we would not have done it," he said.

"We're not in a business where we have to be here to occupy market share or to make volume.

"We're in the business to create value, and Nissan has a very strong policy that all the cars going on the market have to be profitable."

Powerful

It was such unsentimental, straight talk that earned this Brazilian-born Frenchman the nickname "Le Costcutter" when, three years ago, he was wheeled in by Renault to pull Nissan back from the brink.

The French car company holds 44.4% of Nissan's shares.

Among the results of his efforts were the huge efficiency improvements made in Sunderland.

And, off course, he has delivered profits.

In the fiscal year to 31 March, Nissan made record net profits of 372bn Japanese yen (�1.9bn; $3bn), up 12% on the previous year.

Mr Ghosn's performance has elevated him to the position of heir to Renault's president and chief executive Louis Schweitzer who will step down in 2005.

"I said immediately that I would be keeping my job as president and chief executive of Nissan and at the same time become president and chief executive of Renault," Mr Ghosn said.