The council says it is allowed to prosecute residents who fail to separate their waste "without reasonable excuse" under section 46(6) of the Environmental Protection Act 1990.
The scheme will initially be tried in four wards but, if successful, will be expanded to cover the whole borough in October. A Barnet spokesman said that the chances of anyone being prosecuted under the scheme are low.
The scheme has received a mixed response, being welcomed by the Local Government Association but criticised by other councils leading the way in recycling. Steve Beard, head of environmental services at Blaby Council, which charges for side-waste collection, called it an "empty threat" and criticised it for "working against, rather than with, the public."
Barnet's move comes at an apt time. The Government is expected to make an announcement on variable and direct charging for household waste collection later this year.