10% drop in equities 'quite possible' in coming months: Goldman's Oppenheimer

Impact of Brexit has pushed investors up the risk curve: Strategist

Equities in developed markets are once again looking a little expensive, according to Peter Oppenheimer, chief global equities strategist at Goldman Sachs, who has suggested that a 10 percent drop in the asset class could happen in the coming months.

"I think it's quite possible we could get a move up to around 10 percent lower, we thought for a long time that markets are stuck in what we described as a 'fat and flat' range," he told CNBC Tuesday, expanding on a research note published by the investment bank on Monday.

"(Stocks are in) a sort of wide but volatile trading range with relatively low returns. And we think we're at the high end of that trading range and moving towards the lower end is quite likely given the rally that we have seen."

The bank downgraded stocks to "underweight" on Monday as part of its three-month asset allocation. Although it remains "neutral" on equities over a 12-month period and continues its "overweight" position in cash.

Market moves have not been as big as feared: Strategist

The downgrade came after a rally in risk assets over the past few weeks driven by the U.K.'s vote to leave the European Union on June 23 and the search for yield amid expectations of further monetary easing and stimulus measures. Goldman suggested that with equities looking expensive and with weaker-than-expected earnings growth it was the right time to downgrade.

"There's a price for everything, and the valuations now for equities - admittedly perhaps still cheap relative to bonds - is looking pretty stretched when you look at absolute multiples," Oppenheimer added on Tuesday.

"There has to be a limit to how far the market can rise from a valuation perspective with weak growth. On the other hand, there's a limit to how much equities can fall as you continue to see yet lower bond yields and more support, or potential for more support from QE (quantitative easing)."

Market participants have taken a pause for breath in recent trading sessions after the rally. The Dow Jones has been on a losing streak and sentiment in Europe has been hit by volatile banking stocks.

This has led to other analysts questioning the recent run-up, including Tim Drayson, head of economics at LGIM. He believes that better data - particularly in the U.S. - could mean markets sink lower in the coming months and spoke to CNBC Monday on the risk of a "near-term melt-up."

Meanwhile, Sonja Laud, investment director of global multi asset group at Baring Asset Management, believes that August could be a month of relative calm for global equities due to investors kicking concerns over Brexit into the far distance. She spoke of a "vacuum of data" on CNBC last week with only the immediate impact of the vote affecting the U.K., not other developed nations likes the euro zone.

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—CNBC's Spriha Srivastava contributed to this article.