Petty offenders on drugs will be forced to go clean or face a jail sentence in a new pilot project.

Community Safety Minister Fergus Ewing yesterday announced that drug treatment and testing orders, until now only used for serious criminals, would be imposed on less serious lawbreakers in Lothian and the Borders. If it proves successful, it could be extended nationally.

Mr Ewing said the orders, described as "highly invasive", had already proved a popular and successful alternative to custodial sentences for high-tariff offenders. Almost half of addicts who complete the orders stay out of trouble for the next two years.

He said: "We want to build on the current success of drug treatment and testing orders (DTTOs) which can help move problematic drug users into appropriate treatment and support services.

"DTTOs have a positive impact on drug use and offending. After six months on an order, an addict's expenditure on drugs decreased from an average of £490 per week pre-sentence to an average of £57 per week."

Sheriffs have broadly welcomed DTTOs for high-tariff offenders. Last year, nearly 600 were granted across Scotland, one in six of them in Edinburgh. Offenders who do not comply with the orders face prison.

The orders, Mr Ewing said, would be adapted for less serious offenders, especially younger or newer users. "It's not simply a case of extending DTTOs in their present form - the cost, complexity of delivering the order and the fact it has been targeted at more serious offenders means that a slightly different approach is needed. However, if we are successful in our aim it will mean that this group of offenders will not graduate to more serious offending careers.

"Too many of our young people fall into drug abuse and opt out of life. Extending the family of DTTO options could help us catch more of them before they fall too far."

DTTOs do not come cheap. Offenders on them get intensive support at a cost of around £10,000. The alternative, however, is more expensive and rarely as effective: a year in jail, often with no treatment or drugs counselling, costs £35,000.

The two-year pilot is expected to start in the spring and last two years, offering courts an effective option in dealing with offenders at an earlier stage in their drugs misuse.

The theory underpinning the orders is that offending drug users will not stop breaking the law unless something is done to tackle their underlying addiction. The orders do not work for all addicts - they are designed for users who have already admitted they have a problem.

The SNP previously signalled that DTTOs would be extended last summer after a meeting between First Minister Alex Salmond and opposition leaders. Labour and Conservative politicians are understood to be supportive of the move.

John Lamont, Tory Shadow Minister for Community Safety, said: "DTTOs have a role to play in tackling both drugs abuse and crime - therefore we welcome this pilot scheme, especially the adaptation to use DTTOs with lower-tariff offenders.

"However, there are other measures that could be taken as well. We believe that another step must be comprehensive drug treatment and testing orders of every prisoner as they are admitted to prison and at regular intervals thereafter. Today's announcement again does not go that far - this is an objective we will continue to press for."

The Scottish Government is this year expected to unveil the country's first national strategy on illegal drugs.