Cash savings are still overwhelmingly preferred by British people. 

However, those who invest tend to have much higher levels of wealth - even if they are not on a high income, new research has revealed.

The average British adult with savings or investments holds nearly two thirds of it in cash, as opposed to stocks and shares. 

But research from wealth management firm St. James's Place has revealed the wealth gap between those who invest and those who do not. 

Among households earning up to £20,000 a year, investors have wealth worth more than four times that of non-investors, its research claims. 

For the purposes of the survey, wealth includes savings, investments and physical possessions but not pensions.  

Savers in this earning category hold on average £24,559 in wealth, while investors have £103,025 on average. 

It's important to note that many of this number may hold the majority of their wealth within their possessions. 

They could also be pensioners, who have a small income but live off a large pot of savings and investments built up while still in work. 

They may also be self-employed business owners who pay themselves a small salary and take the rest in dividends, while also investing.  

But even among higher earners, who are more likely to be investing from their salary, wealth is much greater compared to those who only save in cash. 

Those earning between £20,001 and £40,000 per year have £133,168 of wealth if they are investors, more than three times the £40,991 held by those who save only in cash. 

Investors who earn more than £80,000 hold wealth, on average, of £528,118 while non investors hold £174,692 - a difference of £353,426, according to St James's Place. 

More than two thirds of those investing for more than five years describe themselves as financially comfortable. This compares with just 26 per cent of non-investors. 

Higher levels of investing may partly reflect the fact that wealthier people are more likely to invest - possibly because they have more financial breathing room if the investment loses value.  

While investing is more likely to produce better returns than saving over a medium to long term horizon, those returns are never guaranteed and the value of investments can fall. It is recommended that you only invest money you don't need access to in the next five years. 

Even wealthier households keep almost £200,000 in cash on average, according to the research. 

Households with investable assets worth between £200,000 and £499,000 hold 40 per cent of that wealth in cash, averaging £116,740. 

Those with between £500,000 and £999,000 keep 36 per cent in cash savings on average which amounts to £197,860. 

Cash might feel like a safe way to store wealth, but its real-terms value - the amount of goods and services it can buy - is eroded by inflation unless it is in an account earning a competitive interest rate. 

Inflation was 2.8 per cent in May this year, so it is crucial to find an account paying more than that. 

The best easy access savings accounts pay interest of up to 5 per cent. You can find them using This is Money's best-buy savings tables. 

Despite this, the average adult keeps most of their investable wealth in cash compared with just 37 per cent invested - equivalent to £52,582 held in cash and £30,673 invested. 

The investment figure does not include pensions.  

Whether you invest or not, it is important to keep some money in an easily accessible cash savings account for a rainy day, with three to six months of living expenses often recommended as a guide.

Alexandra Loydon, group advice director at St. James’s Place, said: 'The long-term investment advantage is clear, yet too much wealth continues to sit on the sidelines, not invested but remaining in cash.

'After several years of economic uncertainty, it is understandable that many households prioritise cash savings because it makes them feel safe and that their assets are accessible. 

'But there is a risk of becoming cash rich but future poor if people remain over-exposed to cash over the long term.'