The two companies removed from the NatWest list are both said to have had inadequate control systems that risked serious financial damage - and one suffered actual losses - from derivatives dealing.
Banks are now routinely examining their clients' internal control systems, assessing whether the management's motives for investing in derivatives are hedging or speculation.
Companies that are speculating as a deliberate policy require much higher internal standards of control.
The concerns have been heightened by a Procter & Gamble lawsuit in the US, followed by what is beginning to look like a deluge of litigation over the $1.5bn derivatives losses by Orange County in California.
US investors that lose money on derivatives have in a number of cases blamed the banks and securities houses that sold them the products for misinformation or selling inappropriate investments.
Although banks are still insisting on the principle of caveat emptor where professional investors are concerned, there is a growing realisation that losses by customers could blacken the image of the derivatives business and encourage greater government regulation on both sides of the Atlantic.Reuse content