The SFO confirmed press reports that some of these may be Madoff-style Ponzi schemes.
The Fraud Office has already made public its investigation of Madoff and of AIG’s UK subsidiary AIG Financial Products Corp, which are included in the seven, but several other investigations are in their preliminary stages and may soon be announced.
The SFO says the suspected frauds may run into hundreds of of millions of pounds and that a proportion of the cases are within the banking sector.
In an Independent interview with SFO director Richard Alderman, the newspaper says the office is likely to make a number of alleged frauds on investors public in the next few weeks.
Alderman says one of the frauds is allegedly a large Ponzi scheme similar to the one used by Bernard Madoff.
An SFO spokesman says investigators are likely to look at the role intermediaries as part of their enquiries, including financial advisers.
He says: “The role of intermediaries is always significant for us to look at, but that is not to say that they have necessarily behaved badly.
“We would look at financial advisers, people working for feeder-funds and professional advisers and other intermediaries.”