An international poll reveals what wealthy individuals consider to be their biggest investment errors before seeking financial advice.

The top investment mistake made by high net worth investors is failure to properly diversify their portfolios (for 27 per cent), according to a survey by financial consultancy deVere Group.

The second biggest error made was not having started investing earlier (cited by 23 per cent), followed by focusing on the short term (20 per cent); being emotional over investments (15 per cent); and not having kept enough cash in reserve (8 per cent). The survey took answers from 652 deVere clients in the UK, Asia, Africa, the Middle East and the US, with investable assets of at least £1 million.

“Ensuring your portfolio is properly diversified is one of the fundamentals of successful investing. Yet it is surprising how many people fail to do this. Having a well-diversified portfolio across asset classes, sectors and regions means you are best-placed to mitigate risks and best-placed to take advantage of important opportunities,” said deVere Group's chief executive and founder, Nigel Green.

Green highlighted the dangers of focusing too heavily on the short term, such as selling a quality investment too early and missing out on potentially longer-term returns.

“Stock market performance is fairly predictable over the longer term – they usually go up. For this reason, investing in equities is recognised globally as one of the optimum ways to accumulate wealth over long periods. If you put off investing you are likely to miss out on the long-term benefits you could have been gaining,” he said.