The Financial Services Authority and City of London Police have found a second boiler room 'suckers list', which contains the personal details of 1,000 investors.
This lists the names and phone numbers of around 750 people along with the names and addresses of a further 250.
The list, which is used by fraudsters to target investors and sell them worthless shares, was discovered as part of Operation WARN.
In February, the FSA and police discovered a master list with the names of around 10,000 investors, some with addresses and phone numbers.
Scammers work for unauthorised, overseas-based companies with bogus UK addresses and phone lines routed abroad.
They usually contact people by telephone and use high pressure sales tactics to con investors into buying non-tradable, overpriced or even non-existent shares.
Investors who are duped into parting with their cash are not eligible for the financial complaints and compensation schemes.
Jonathan Phelan, head of the unauthorised business department at the FSA, says: "This is the second master list we have obtained in as many months. Our sources indicate that the list is a new one and still in use by the fraudsters, so by contacting people on it we hope to cut these boiler rooms off at the pass.
"Raising awareness of this type of fraud through publicity is one of the best tools we have to prevent people getting involved and losing their money. Legitimate share dealers and brokers will not normally cold call people offering to buy or sell shares, so if you get one of these calls - just hang up and report it.
"The key message remains: if it sounds too good to be true, it almost certainly is."
Anyone offered shares should check to ensure the company selling them is registered with the FSA. They should then call the company back using the details on the watchdog's website to verify their identity.
The FSA and City of London Police have launched a new secure consumer helpline on 0845 602 2185.