Communities have overwhelmingly praised the work done by offenders undertaking community service - but councils have warned it comes at a cost.

The community payback order (CPO) was introduced in 2011 as an alternative to prison.

Last year, offenders carried out 1.3 million hours of unpaid work such as litter-picking, graffiti-cleaning, gardening, gritting and craftwork, according to a Scottish Government summary of council CPO annual reports from 2014-15.

A "recurring theme" throughout the reports was the pressure the increase in CPOs is putting on council resources, particularly where the offender does not speak English as a first language due to the requirement for an interpreter.

Welfare reform is also having a "significant impact" on the workload of social workers, who are being called upon to give financial advice and deal with clients whose benefits have been stopped.

The report states: "The majority of local authority reports highlighted overwhelmingly positive feedback received from communities for the unpaid work that was carried out in their areas.

"This was received from the beneficiaries of the unpaid work, expressing their gratitude for the high standard of work carried out and the positive attitude of individuals on CPOs and their supervisors."

Offenders also expressed gratitude for "the stability unpaid work has brought to their sometimes chaotic lives, along with the skills and confidence they developed".

The most frequently imposed CPO requirement is an offender supervision order.

The report states: "Some local authorities noted that there has been a steady increase in the number of offender supervision requirements imposed as part of a CPO, which they have found a challenge, particularly given the impact that this has on resources."

It added: "A recurring theme throughout the reports was the pressure that an increase in the number of CPOs, particularly those which contain an offender supervision requirement, put on existing resources.

"Some local authorities also considered that there was an increased pressure given the expectation for individuals to commence unpaid work immediately

"In addition, some local authorities noted the increasing levels of individuals for whom English is a second language and the impact that this can have on resources given the increased need for interpreters."

It continued: "Welfare reform, and particularly 'sanctioning', continues to have a significant impact on some individuals, with many having their benefits stopped for missed appointments.

"Criminal justice social workers (CJSW) continue to work with partners to minimise the impact this has on more vulnerable individuals.

"Also, it has been noted that there continues to be an increase in requests for financial advice and assistance with benefit claims."

New psychoactive substances (NPS), often referred to as "legal highs", have presented "a significant challenge".

The report stated: "This changing nature of substance use by some individuals can make it difficult for treatment services to address these issues."

Housing also presents "a significant problem for individuals and CJSW services".

"Individuals receiving CPOs can sometimes lead chaotic lifestyles which can often be exacerbated by a lack of stable accommodation," it stated.