Mr Quattrone resigned from Credit Suisse First Boston (CFSB) by mutual agreement three days ago after refusing to testify to a regulatory inquiry into destruction of documents at the bank.

One of the "Friends of Frank" made about $1.3m - the return... was 58,000% Barry Goldsmith, NASD

The latest charges of misconduct could see Mr Quattrone banned from working in US investment banking if found guilty by his professional regulator.

The National Association of Securities Dealers (NASD) has filed to two complaints against him, relating to the promotion of lucrative technology stocks in the late 1990s.

'Cash gifts'

The first alleges that Mr Quattrone kept a list of about 300 favoured clients - known as the "Friends of Frank" - whom he helped to benefit from rapid rises in the price of new share issues during Silicon Valley's boom era in the late 1990s.

As head of CSFB's Global Technology Group, Mr Quattrone handled shares in sought-after new listings by hi-tech firms.

The "Friends of Frank" were senior executives of CSFB's client companies who were allocated shares in these listings, guaranteeing them big profits.

The practice was "tantamount to giving them cash gifts" and violated NASD rules, the charge said.

"One of the 'Friends of Frank' made about $1.3m, the return... was 58,000%," said Barry Goldsmith of the NASD on BBC World Service Radio.

Research 'compromised'

Mr Quattrone is also accused of encouraging his team of analysts to issue overly-enthusiastic research on technology firms, thus ramping up the price of their stocks.

The structure of the Global Technology Group he ran was "inherently flawed", said Mr Goldsmith, adding that "the objectivity of the research analysts were compromised".

The second charge relates to Mr Quattrone's failure to testify at an inquiry into CSFB where investigators wanted to ask him about suggestions that he ordered staff to destroy documents.

'Baseless and unfair'

Mr Quattrone's lawyer has said the charges are "completely without merit" and "an unprecedented attempt to take punitive action against an individual" for widespread practices that were legal at the time.

CSFB has been targeted by officials investigating some of the most famous recent Wall Street scandals, including the collapse of Enron, and the ramping up of fees during the dot.com boom years.

CSFB paid fines of $150m as part of a settlement with other banks, agreed with state and federal regulators investigating potential share research and stock allocation abuses.