Prudential said it was actively searching for a replacement for Hugh Jenkins, who is formally retiring from the company on New Year's eve.
Until a new chief executive at PPM is found, Mr Jenkins' place at the helm will be taken by Rodney Dennis, currently managing director of the fund management company's UK and European arm.
Mr Dennis, who joined the company in 1987 to head its international equities team, is believed to be one of the favourite internal candidates for the top job although outside applicants will also be interviewed.
However, a Prudential spokeswoman said no timetable was being set for an appointment: "We will take whatever time is needed to ensure that the right candidate is selected for what is a vitally important job within the group."
Whoever succeeds Mr Jenkins will have one of the most powerful jobs in the country, so important that in a poll 12 months ago of the most important 100 people in the UK, he came in 22nd, several places above Mick Newmarch, then the Pru's own chief executive.
The job's importance lies in the fact that it determines the overall investment strategy of the Pru's pounds 75bn under management, including more than pounds 30bn in the UK life fund.
Every day a further pounds 10m is paid into the fund from investors, including millions of endowment and pension plan holders.
Mr Jenkins joined Prudential in 1989 after three years as group investment director at Allied Dunbar, another big insurer. Before briefly working in the United States, he spent 23 years at the National Coal Board's pension fund, where he rose to become director general.
In the past year at the Pru, Mr Jenkins has helped steer its fund management arm into backing the changes proposed by the Cadbury Committee on corporate governance.
However, he has argued that the newly-formed "Cadbury Two" committee should not go further than monitoring the implementation of changes put forward in the first report.
He has also spoken in favour of "realistic market salaries" for directors, albeit linked with company performance.
Despite his retirement, compulsory for all senior Prudential executives at age 62, Mr Jenkins is expected to remain a non-executive director of Thorn EMI, the electronics group, and Rank, the leisure giant.
His temporary successor, Rodney Dennis, is chairman of PPM's asset allocation committee, playing a key role in the overall investment strategy for the funds managed by PPM.
Mr Dennis, who is in his 40s, also chairs PPM's UK equity policy committee, which is responsible for UK investment strategy.Reuse content