US regulators have suspended and fined two senior executives at investment bank Credit Suisse First Boston for allegedly ramping up brokerage fees during the dot.com boom.

The National Association of Securities Dealers on Thursday suspended CSFB's head of equity sales, J. Anthony Ehinger, and George Coleman, its chief listed institutional sales trader, for two months, and fined them $200,000 each.

Four former CFSB employees who specialised in technology investments on behalf of private clients were suspended for one year and fined $30,000 each.

The NASD's decision to penalise the executives follows a probe into allegations that CFSB staff charged clients huge premiums in return for guaranteed allocations of highly-sought after new technology share issues.

In January, CFSB paid $100m to settle an inquiry into the affair conducted jointly by the NASD and the Securities and Exchange Commission, the main US stock market regulator, but did not admit guilt.

Tech boom fall-out

CFSB said on Thursday that it had taken "internal disciplinary action" against the employees involved after settling the investigation.

It was alleged that the bank's executives took advantage of strong demand for newly-issued technology shares to levy excessive brokerage fees from clients keen to acquire a stake in the much-vaunted 'new economy.'

CSFB is not the only Wall Street giant to have been taken to task its activities during the late 1990s technology boom.

Earlier this year, New York prosecutors launched a probe into allegations that analysts at Merrill Lynch issued glowing research reports on firms they privately disparaged so as to gain lucrative banking contracts from them.

In May, Merrill paid $100m to settle the investigation without admitting any wrongdoing.