A writ, filed in a Manhattan court, alleges that Facebook's revised growth figures were not disclosed to all investors.
US financial regulators have already said the Morgan Stanley may have questions to answer over the disclosure of information ahead of Friday's float.
The bank, lead underwriter to Facebook, said it fully complied with the rules.
The lawsuit claims that defendants concealed from investors during the flotation marketing process "a severe and pronounced reduction" in revenue growth forecasts.
Meanwhile, the Reuters and AP news agencies reported that the Senate banking committee may look into the matter, but was still considering its options.
These latest developments continue to cast a cloud over one of the most anticipated stock market listings of recent times.
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