According to analysis from data provider Moneyfacts the performance was the worst since the financial crisis in the 2008/2009 tax year when equity Isas fell by 20.3%.

In contrast the average cash Isa grew by 1.21% in the 2019/20 tax year.

Despite the fall in stocks and shares Isas the average equity Isa has done well in 14 of the 21 tax years since the introduction of Isas in 1999, said Moneyfacts. And while equity Isas lost money on average in 2019/20 this followed three consecutive tax years of growth.

Only two previous tax years have seen heavier falls: 2002/03 (-19.7%) and 2008/09 (-20.3%).

In terms of fund sectors, UK equity funds were badly hit in the last tax year. The average UK Equity Income fund fell 26.9%, UK All Companies funds fell 25.5% and UK Smaller Companies funds dropped by 20.6%.

European Smaller Companies (-20.6%) and Japanese Smaller Companies (-23.6%) were the only other fund sectors that posted comparative losses. By contrast, UK Gilts (12.2%) and Global Bonds (6.7%) were the best-performing ISA fund sectors, said Moneyfacts.

Richard Eagling, head of pensions and investments at Moneyfacts, said: “These are extraordinary times for investors, as shown by the fact that cash ISAs outperformed the average stocks & shares ISA in the 2019/20 tax year.

“The Coronavirus pandemic means that stock markets are experiencing unprecedented volatility and investment returns across most fund sectors have naturally been hit hard. As dismal as the last tax year has proved to be for investors, it is unlikely to dampen enthusiasm for stocks & shares ISAs too much, as their long-term case remains compelling.”