Craigs Investment Partners broker Peter McIntyre said a vote to leave the European Union would be negative for the pound.
The considerable uncertainty investors would face would most likely result in a temporary halt in foreign investment in the UK.
Should the UK elect to remain in the EU, a strong relief rally in the pound should follow as the market priced in a more certain investment backdrop, he said.
The pound tended to act as a pro-cyclical currency, appreciating when economic growth and markets were strong.
"We expect global growth to remain modest and for cyclicals to continue to underperform defensive sectors.''
The UK ran the largest current account deficit among all major developed market economies because it imported far more than it exported. Combined with high levels of government and private sector debt, that resulted in a high reliance on foreign capital, Mr McIntyre said.
There was a strong relationship between the UK economy and house prices and housing-related activity. There were clear indications house prices and housing activity in the UK were losing momentum.
As a result, Craigs expected the pound to perform poorly relative to all major developed market currencies - even before taking into account the potential exit from the EU.
Mr McIntyre warned the Brexit vote could start a wider debate on the future of the euro as other countries consider leaving the EU.
Germany, which had felt the benefits of a lower euro through its export sales, would start to ask why it was still in the EU when it had borne the cost of the bail-outs. France was already talking about leaving.
British Prime Minister David Cameron had warned against inflation rising if Britain left the EU but many countries would welcome some inflation, no matter how it came, Mr McIntyre said.
"The whole EU is starting to to unravel. We expect an impact on the financial markets - not a Global Financial Crisis scenario, more of a liquidity issue. Each country will start looking for their own little currency cushion.''
The UK sharemarket remained dominated by multinational companies with little underlying exposure to the UK economy. Any impact to the UK economy as a result of the referendum outcome was unlikely to materially affect UK sharemarkets in the medium to long term. However, a vote to leave the EU would likely result in a short-term sell-off in UK markets, he said.
Asked if that would create a buying opportunity, Mr McIntyre said many investors bought UK equities without considering the implicit sector biases in the UK sharemarket. To take a positive view on UK equities, investors must be comfortable being overweight in energy, materials and European financials.
"Our view remains the UK will continue to underperform other developed markets primarily because of the inherent sector biases to deep cyclical companies and lower quality financial institutions.''
