The OBR said a three-month lockdown followed by three months of partial restrictions would trigger an economic decline of 35.1% in the quarter to June alone, following growth of 0.2% in the first three months of this year.
The Office for Budget Responsibility (OBR) said that this was based on an assumption that the current lockdown would last for three months.
Once restrictions are lifted, the OBR expects no lasting damage to growth.
Separately, the International Monetary Fund warned the virus would push the UK into its deepest slump for a century.
The UK’s independent tax and spending watchdog has warned the coronavirus pandemic could see the economy shrink by a record 35% by June.