Criminals will face more intense hours on tasks like cleaning graffiti
Criminals sentenced to community service may have to work full-time under new government rules.
The Ministry of Justice says more serious knife and drug crime offenders will face intensive blocks of work of up to five days a week.
It could be extended to all offenders given community service, if a pilot scheme in West Yorkshire is rolled out.
The shake-up follows Prime Minister Gordon Brown's pledge to make community payback tough, visible and effective.
Justice Minister David Hanson said: "Offenders sentenced to 'pay' for their crimes within the community can already expect to work hard and lose much of their free time.
"By introducing intensive five-days-a-week payback for many knife crime offenders we are further toughening these punishments."
Initially the changes will affect people sentenced to the maximum 300 hours community service - but the pilot scheme will include those given 200 hours.
Mr Hanson added: "It is important that the public can see and influence the work that is being carried out by offenders in their neighbourhoods.
"This is crucial to ensure that there is confidence in community sentences."
Last year 55,771 community payback sentences were completed across England and Wales.
Offenders are ordered to carry out work such as picking up litter, renovating community centres and clearing undergrowth and graffiti for local communities.
Recent statistics show the number of people given community sentences who re-offend has fallen sharply by 13%.