A massively botched trade by a Japanese stockbroker sent the Tokyo market into turmoil today and left his company facing heavy losses - and the ire of its trading rivals.

The trader, who worked for Japanese investment house Mizuho Securities, mistakenly placed an order to sell 600,000 shares in J-Com, a recruitment firm whose shares were making their market debut today.

The "fat-fingered" sell trade - when he had intended to offload a fraction of that amount - represented a staggering 41 times the amount of shares in the company that were actually available to the entire market.

In the ensuing confusion, shares in J-Com initially tumbled as the market tried to identify the source of the trading error. Concern about possible mistakes at trading houses with lax risk controls sent banking stocks diving and then hit the wider Tokyo market.

It was initially unclear which firm had sparked the frenzied selling, with a spokesman for the Tokyo Stock Exchange saying only that it was aware a trade had been made that "is hard to comprehend".

A red-faced Mizuho Securities only admitted being behind the trade after the Asian markets closed at the end of the day's trading.

But this was after the broker's mishap left the benchmark Nikkei stock market index nursing its third-largest fall for the year.

"We sincerely apologise for causing considerable trouble for those concerned," Mizuho said. In a statement, it said it was investigating the incident and was in talks with the exchange about what happened.

Yasuhiko Okamoto, the president of J-Com said he - and float underwriters at Nikko Citigroup - had been told by the Tokyo Stock Exchange of the embarassing mistake.

Shares in his company subsequently recovered to close up at the end of the trading day.

But other dealers were not amused. One head of equity derivative sales at a major American brokerage in Tokyo told Dow Jones: "We're clearly working in Disneyland today."

The debacle holds echoes of similarly expensive "key stroke" errors that can be highly costly for the brokerages involved. In 2001, Swiss-American investment bank UBS mistakenly sold 65,000 shares in advertising group Dentsu, which was also making its market debut.

Dentsu subsequently had to buy most of the shares back from the market.

Similar problems have occurred in the past, if rarely, on the London market, although it in most cases the identify of the perpetrators remains a mystery - except to themselves and the heads of their trading desks.

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