Asset manager Threadneedle has dismissed a junior trader after internal controls picked up an attempted rogue trade

City of London police are investigating a suspected $150m (?95m) trading fraud that was foiled at Threadneedle, the asset manager spun out of the tobacco and insurance giant BAT Industries.

A junior trader has been dismissed following an attempted rogue trade that was discovered by internal company controls and blocked last year.

In a statement, Threadneedle said: "In August 2011, our systems stopped a suspicious attempted trade. The matter was immediately reported to the authorities and the individual involved was subsequently dismissed."

The trade was thought to be linked to Argentine warrants, which pay holders when economic growth exceeds government projections, although it is understood that no client money was lost.

The incident at Threadneedle ? the London-based subsidiary of US financial services group Ameriprise which has around ?60bnunder management ? is the latest in a series of alleged rogue trading scandals that have emerged in the City. Last year Kweku Adoboli, a former UBS trader, was arrested after being accused of causing "unauthorised" trading losses of $2bn ? which would be the largest rogue trade uncovered in City history. He is expected to face trial this year and denies charges of fraud and false accounting.

Last week, a 44-year-old Legal & General employee was arrested as part of a wide-ranging investigation by the Financial Services Authority and the Serious Organised Crime Agency into insider dealing.

The cases follow high-profile dawn raids in March 2010, when the FSA arrested six men in part of its biggest ever crackdown on insider dealing. At the time around 143 police officers and FSA staff were required to conduct the raids, which the authority described as its "largest-ever operation against insider dealing".