"However, in the past three months money has been coming out of markets, and deposits into cash are up."
Mr Gregson added that cash was the only asset class that could fulfil the remit set to him by many clients at the moment: not to lose capital.
Such is the market uncertainty that Barclays is allocating a substantial 45pc of low-risk investors' portfolios to cash. Move up the risk appetite scale and the proportion is reduced to 12pc for those who want moderate risk and 7pc for those who have high tolerance.
Barclays uses a mixture of floating-rate notes, short-term bonds and instant-access accounts for its clients' cash allocation – with at least half of the money in instant-access accounts for liquidity purposes.
Mark Dampier of Hargreaves Lansdown, the advisory firm, said cash was the more attractive asset for investors right now.
"While many cash accounts fail to beat the rate of inflation, at least your capital is protected if you keep it in cash," he said. "It may be an unpopular view among advisers, but the markets can lose you money."
Mr Dampier added that although fixed-rate accounts might offer a greater return on your money than the "cash park" facilities found on fund supermarket platforms, the most important thing about today's market conditions was keeping your assets liquid.
Cash parks allow investors to "park" their cash before investing it in an Isa, protecting its tax-free status and buying the individual more time to choose which fund to invest in. You can then return to the investment platform when you consider there is a worthy investment opportunity and transfer your money into a stock or fund without losing its tax-efficient status.
The cash park on the Hargreaves Lansdown platform pays 0.25pc for deposits of more than £50,000, 0.1pc for less. Fidelity Fundsnetwork's cash park facility pays Bank Rate minus 0.2 percentage points – currently 0.3pc. Bestinvest's facility pays 0.25pc on deposits of more than £20,000, but nothing for smaller sums.
Mr Dampier said: "The market moves so much at the moment that there may be a buying opportunity today that has passed in a week. If your cash is locked away in a 30-day notice account, that is no good," he said.
"Yes, you may not get an inflation-beating return in the cash park, but your capital is protected and your portfolio liquid."
While savers' fears about investing in the market are well founded, Adrian Lowcock of Bestinvest urged them to steel their nerve if they could.
"There is no doubt that the uncertainty in Europe, particularly around the Greek elections, has put investors off. It is important that, if you do put cash aside in an Isa or Sipp while waiting to invest, you actually take action and invest it. Don't forget about it," he said.
"It is human nature not to act in times of crisis. Ultimately when investing they buy high and sell low, when in fact they should be looking for the longer term and buying on weakness, not waiting for a rebound."
The euro crisis has hit this year's Isa investors hard and their caution is understandable. Last week The Daily Telegraph's Your Money section disclosed that many savers will have seen as much as 25pc wiped off the value of their fund in just three months as global economic fears intensified.
Several of the biggest and most popular funds have been hardest hit. Aberdeen Emerging Markets, for example, was one of the best-selling Isas in the run-up to the end of the tax year. But anyone who invested £10,000 in mid-March would now be sitting on a fund worth £9,156, according to Morningstar.
An investor who bought the popular JP Morgan Natural Resources fund would have seen a £10,000 investment fall by almost £2,500 to just £7,683 – which means that the fund needs to climb by more than 30pc from here just for savers to break even.
And there is little sign of relief on the horizon despite the Greek election result, which did not rule out the threat of the country exiting the euro.
Fund managers are in a cautious mood, too. A survey of 260 asset managers across the globe by Bank of America Merrill Lynch found that cash positions rose to 5.3pc in June, levels similar to those seen at the height of the financial crisis in January 2009 and the highest since March 2003 and December 2008.
Falling sipp rates
The rates paid on cash by Sipp providers have come in for criticism in the past – last year several financial advisers branded them as "unacceptable".
Investors who choose to keep Sipp allowances in cash frequently earn Bank Rate (0.5pc) or less; the average rate is just 0.75pc, according to Investec Bank.
With inflation still riding high at 2.8pc, this gives negative real returns for hundreds of thousands of pension investors.
Advisers said that on average investors held almost 10pc of their Sipp in cash. Investors are allowed to deposit £50,000 or 100pc of their salary a year into a pension, whichever is the lower. This means that potentially £5,000 a year of pension savings is guaranteed to be eroded by inflation.
The average amount of cash held in a Sipp is £39,000, Investec said, with some investors having as much as £50,000 in cash – built up over years of pension contributions.
Lionel Ross of Investec said: "The stagnant Bank Rate is having a knock-on effect on the rates paid on the cash element of Sipps. Advisers are now waking up to the need to challenge their current cash account provider to ensure that their clients are getting the highest possible returns on their deposits, which should in turn enhance overall pension fund performance.
"Given ongoing market volatility, investors, particularly those nearing retirement, are increasing their cash allocation. However, it is essential that they check that this money is held in an account paying a competitive rate of interest."
Around £90bn is held in Sipp accounts nationwide.
Not all Sipp cash rates are bad, however. Investec's own offering pays 2.25pc for sums of £25,000 or more. James Hay Partnership pays between 1.4pc and 2.9pc, and Hargreaves Lansdown said it offered fixed deals paying up to 2.5pc for Sipp holders who wanted to hold cash for three months or more.
But Darius McDermott of Chelsea Financial Services warned investors to avoid cash funds. "There are funds that invest in cash or cash equivalents but other than providing more of a 'safe haven' for your money, as they invest across more than one financial institution, they offer little incentive at the moment. Most are returning only in the region of the Bank Rate so you'd be better off in a bog-standard savings account," he said.
Moneyfacts, the financial information service, said a higher-rate taxpayer would need to find an account paying at least 4.7pc to negate the impact of tax and inflation. However, there are few accounts available that will pay this much, meaning that once people have exhausted their Isa allowance they will struggle.
Basic-rate taxpayers have more luck, with 210 accounts that overcome both the effect of inflation and the taxman's cut by paying 3.7pc or more.
Birmingham Midshires has a three-year fixed-rate bond that pays 4pc and can be opened with a deposit of just £1. Secure Trust Bank's five-year fixed-rate cash bond requires a larger deposit of £1,000 but pays an impressive 4.45pc.
The best one-year bond on the market is from Cahoot and pays 3.6pc. For instant access go to
santander.co.uk – the bank's online saver account pays a market-leading 3.2pc and can be opened with £1.
