The S&P/ASX 200 index could retest the 5000-point level if negative momentum continues, according to an analysis of technical levels.

The benchmark was trading about 5180 on Wednesday afternoon, down 0.5 per cent from Tuesday's close. The market has dropped about 4 per cent from late May's highs of 5400, thanks largely to fears Britons could choose to leave the European Union in next week's landmark vote.

"The S&P/ASX 200 index now joins other key global indices – Dow Jones, FTSE, Eurostoxx50, DAX and CAC – which activated technical sell signals on Tuesday night," said QMG technical analyst Angela Mangan.

The next technical support level was about 100 points lower, she said.