The Prime Minister will officially announce the changes today Wednesday 9 September.
Social gatherings of more than six people will be illegal in England from Monday 14 September as the Government seeks to slow the rise in coronavirus cases.
The current limit is 30 people.
Those breaking the rules will face a £100 fine, doubling after each further offence up to £3,200.
Exemptions will include weddings, funerals, work places, schools and university lectures and Covid secure team sports