A former top agency manager at Prudential Assurance Company Singapore breached his agency agreement by soliciting more than 200 agents and leaders to jump ship to rival insurer Aviva, the High Court has found.

Mr Peter Tan Shou Yi and his company, PTO Management and Consultancy (PTOMC), were sued by Prudential for up to $2.5 billion for allegedly "surreptitiously" orchestrating a mass defection of 244 agents and leaders to Aviva subsidiary Aviva Financial Advisers in mid-2016.

The move left 70,000 policies without agents.

Mr Tan provides services to Aviva through PTOMC, a corporate vehicle he owns that receives bonuses and benefits from Aviva to recruit new agents.

The High Court held that Mr Tan, 56, is liable for breach of his contractual obligation to "conduct his insurance business with integrity and honesty".

This clause required him to serve Prudential with "good faith and undivided interest" and "included a duty not to solicit (Prudential's) agents" during the agency agreement "to join a competitor", Justice Chua Lee Ming wrote in a 132-page judgment released yesterday.

The court found that Mr Tan discussed with Aviva an arrangement whereby he would "procure" agents in Peter Tan Organisation (PTO) to leave to join Aviva. It was then the biggest and most successful group of agents selling insurance products for Prudential.

He also solicited his agency leaders to leave and asked them to persuade other PTO agents to do so.

PTO, which had about 500 agents in 2016, contributed about 10 per cent of Prudential's entire agency force sales at the time.

The 244 agents who defected included 241 from PTO.

Mr Tan gave a 14-day notice of termination on July 8, 2016.

Prudential estimated that the amount it would have earned if Mr Tan had stayed on to manage PTO until 2019 would be around $103 million. If PTO had remained with Prudential in perpetuity, the potential profits would have amounted to $2.3 billion, The Straits Times understands.

The timeframes were taken in view of an agreement that Mr Tan signed with Prudential just a year before the mass defection that contained projections of his and his agents' performance for at least 10 years.

But Justice Chua found that Prudential's claim for loss of profits beyond the initial six-year term of the agreement was "too speculative".

He found that of the 244 departed agents, Mr Tan was liable only for profits that Prudential could have earned from 227 - 204 agents and 23 agency leaders - from May 9 to July 23, 2016.

Prudential's claims for losses suffered for the remaining 17 agents were dismissed.

The assessment of losses will be calculated by Queen's Counsel Richard Boulton, who is also the chairman of British consultancy Berkeley Research Group.

Justice Chua also dismissed Prudential's claim that Mr Tan had breached his fiduciary duty because Prudential "did not entrust him with the management and control of the agents in PTO".

Since he did not owe Prudential any fiduciary duty, its claim against PTOMC for dishonestly helping him to breach his fiduciary duties was dismissed.

Counterclaims filed by Mr Tan against Prudential were all dismissed. He told ST yesterday that most of the claims against him were dismissed, as were all claims against PTOMC.

"The court did find a breach and that I have to pay for about 2.5 months' worth of loss," he noted. "This still has to be calculated, but I think it's likely to be less than half per cent of Prudential's claim."

His lawyers are studying the judgment "so that I can consider all my options".