Volkswagen (XETRA: VOW3-DE) may be an even bigger risk for investors than previously thought, as a key part of its business -- aside from making cars -- is threatened by the diesel emissions scandal.

The company's financial services business, which gives consumers loans to buy its cars and accounts for close to half of its balance sheet, could be the next source for alarm, according to analysts at Credit Suisse. The previously successful business -- which currently has more than 100 billion euros of outstanding loans to customers -- may even need fresh capital, the analysts argue.

"We increasingly see risk in VW's Financial Services business which supported industrial growth in the past. Higher refinancing costs and risk provisioning makes it difficult for the financial services business to fund itself going forward; thus a capital injection would likely be required unless growth is reduced materially," Credit Suisse wrote in a research note Friday morning.

In other words, the woes of the manufacturing arm of the business are likely to affect the financial services' ability to borrow to fund its operations.

VW's borrowing costs, measured by its bond yields, are already up by 200 basis points since the company admitted lying about diesel emissions in mid-September.

If it is more difficult to get a loan to buy a Volkswagen as a result, the number of consumers wanting to buy its cars may dwindle even further.

The financial services arm has been expanded to fuel the growth of the manufacturing arm, which had ambitious targets to overtake Toyota as the world's biggest carmaker before the catastrophic revelations.

The beleaguered car maker's share price, which has lost around two-fifths of its value since the news of the emissions falsification, fell by 2 percent in early trading Friday.

- By CNBC's Catherine Boyle

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