Small investors have been spending lockdown taking punts on volatile stock markets, boosting trading at online investment firms IG Group and AJ Bell.

IG Group said pre-tax profits surged 52% to £296m over the year to May, after average daily trade volumes reached 1m at the peak of the Covid-19 market sell-off in March. That is three times higher than average trade volumes of 336,000 recorded a year earlier.

The firm said it attracted 96,900 new customers over the financial year, while the number of active customer traders rose 34% to 239,600. It helped the trading platform, which makes most of its income from transaction fees, record a 36% rise in net trading revenue to £649m.

While some customers will have lost money on their market bets, IG stressed that it “does not benefit from client trading losses, nor is it exposed to client trading profits.”

Investment firm AJ Bell said it brought in another 20,370 platform customers in the three months to 30 June, pushing its total customer pool up 8% for the quarter to 282,619.

AJ Bell said assets under management linked to its platform business reached £47.7bn, an increase of 10% from a year earlier and 14% over the quarter. It now expects full-year pre-tax profits to beat expectations by at least £2.5m. Analysts were forecasting annual profits worth £43.4m.

Both companies have benefited from a surge in customers chasing returns during the Covid-19 lockdown, after the Bank of England cut interest rates to record lows of 0.1% in March.

The AJ Bell chief executive, Andy Bell, said: “Markets have rebounded from the lows seen in the previous quarter but remain volatile and this has helped increase the value of assets under administration and customer trading volumes.

“Our focus throughout the Covid-19 crisis has been on ensuring we are here for customers and advisers when they need us and this has translated into strong net inflows onto the platform and continued strong organic growth in new customers.”

But both IG and AJ Bell are predicting a slowdown in trading as markets start to stabilise over the coming months. IG said activity had slowed since its March peak and that it was expecting market volatility to return to “more normalised levels” over the next financial year.

However, they are no longer facing extra competition after the controversial investment app Robinhood cancelled plans to launch in the UK.