It’s clear that investors are uncertain what to do in the wake of Britain’s decision to leave the European Union.

Share markets around the world plunged on Friday and into the early hours of Saturday, before the S&P/ASX 200 (Index: ^AXJO) (ASX: XJO) enjoyed a relief rally on Monday. Further falls in international equity markets overnight, however, have led to another sharp decline in local shares today with investors still uncertain what the future will hold.

Indeed, many investors will also be wondering whether now is the time to buy, or sell shares. While that topic was discussed more broadly here, it’s worth taking a closer look at a few companies which you may want to steer clear of, for now…

One company that has been hammered since Friday is Clydesdale Bank plc (ASX: CYB). The UK-based bank was spun-off from National Australia Bank Ltd. (ASX: NAB) earlier this year. Clydesdale Bank operates in both England and Scotland.

Indeed, the company’s share price has been battered in the days since the referendum vote and may present a buying opportunity in the near future if its shares continue to fall. This is particularly the case since there will be no immediate fallout from the decision (the divorce process could take at least two years), while the terms of any new economic relationship are also yet to be determined.

However, given the uncertainty facing the European market right now, Clydesdale Bank shares may not be suitable for risk-averse investors.

Many economists expect central banks around the world to provide more stimulus (i.e. lower their cash rates) in response to the heightened uncertainty, which would also be bad news for QBE Insurance Group Ltd (ASX: QBE).

Insurers charge a premium from clients wanting to transfer their risks, and then invest the float which is typically a key source of earnings. However, lower interest rates would limit that earnings potential. What’s more, QBE operates in the European markets, which does raise questions about how it will operate its business in the future.

It recently said: “The referendum outcome may require a revised approach in relation to approximately GBP500 million of insurance and reinsurance premium that QBE currently sources from EU member countries that is written via branches of UK regulated entities under current EU passporting rules.

BHP Billiton Limited (ASX: BHP) is another business that investors might want to avoid. The future was already unclear for the prices of many commodities considering the demand and supply imbalance, and that may be exacerbated by Britain’s decision to leave the EU.

Again, any economic changes from Brexit mightn’t come to fruition immediately but it could hinder the growth outlook in some countries. Commodities such as iron ore, coal, copper and petroleum – which are BHP’s ‘four pillars’ — could be impacted if this growth were to subside, which would be a bad thing for the business, and its share price.

3 (more) Rotten Shares to Sell, and 1 to Buy Today

After Britain's shock exit from the European Union, investors are right to be cautious. You'll find a full rundown below of 3 shares we think you should avoid today plus one top pick worth buying, even if the market turns south and the RBA keeps rates at an "emergency low." Simply click here to uncover these stocks.

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Motley Fool contributor Ryan Newman has no position in any stocks mentioned. The Motley Fool Australia has no position in any of the stocks mentioned. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy. This article contains general investment advice only (under AFSL 400691). Authorised by Bruce Jackson.