According to the Daily Telegraph, one of UBS's analysts sent an email containing details of the price at which GM shares would list on the markets, to 100 people by mistake.
The gaffe has led GM to disclose in regulatory filings that there is now a risk that buyers of shares "may have the right to seek refunds or damages" if the email is found to have broken laws governing share sales, according to the Financial Times newspaper.
The FT said, though, that GM claims that it will not "be subject to any material liability as a result of the distribution of the e-mail".
The car maker is undertaking a stock flotation to raise $10 billion to pay back some of the money it borrowed as part of a US Government-funded bail out.
UBS confirmed to the FT that it was no longer part of the underwriting syndicate. A fee of 0.75% was due to be shared by the several underwriters to the deal, and industry estimates put the share that would have been due to UBS at $10m.
