Thousands of trials a year could be prosecuted by non-lawyers under plans for an extension of the powers of the Crown Prosecution Service?s lay staff.

Proposals about to come before MPs would enable CPS staff without legal qualifications to conduct ?not guilty? trials in magistrates? courts, such as theft, assaults, applications for bail or antisocial behaviour orders.

The plans have been condemned by the Law Society of England and Wales, which accuses the Government of ?prosecuting on the cheap and putting victims of crime and witnesses in peril?. They also say that victims of crime may be deterred from allowing cases to go ahead if they fear they will not be handled properly.

But Sir Ken Macdonald, QC, the Director of Public Prosecutions, has robustly defended the move to devolve work, arguing that it is part of a wider trend across the professions. He told The Times that the use to date of some 400 lay CPS staff to handle simple cases had been a success, freeing qualified lawyers to deal with serious and difficult cases and cutting trial delays. He insisted that he could not imagine any situation in which the case workers would be entrusted to handle cases where a defendant might go to jail.

At present, ?designated case workers? in the CPS have power only to conduct a limited range of simple cases where defendants plead guilty ? many of them road traffic offences.But clause 58 of the Criminal Justice and Immigration Bill would widen their powers, where approved by the Director of Public Prosecutions, to conduct ?not guilty? trials, including the more serious offences that could be tried by judge and jury but where defendants elect for trial by magistrates. Offences include a range of assaults, drugs, public order, shoplifting, thefts and driving offences.

The case workers would also be able to handle contested bail applications and applications for a range of orders including Asbos, parenting orders, restraining orders, and drinking and football banning orders.

The Law Society has expressed concern to MPs about the measures, due to come before the Commons for their second reading next week. In a briefing paper it says that it does not oppose deploying paralegals in appropriate cases as this ?will result in the time of legally qualified prosecutors being more productively used?. But it adds: ?Allowing designated case workers to undertake summary trials or contested bail applications in relation to serious offences is inappropriate.?

With the numbers of legal-aid defence lawyers at risk because of the proposed changes to the ?2 billion legal aid scheme, there is a danger, the society says, that trials will take place without ?anyone legally qualified in court when a defendant is facing an imprisonable offence?. The case workers were not subject to any professional code of conduct, nor, like lawyers, under a duty to the court, it adds.

It also has concerns about lack of training. ?They receive limited initial training, which we understand consists of a two-week residential course, and continuing training. The proposal is not aimed at improving the quality of the service provided to victims of crime and witnesses . . . but rather an expedient to save money.?

Des Hudson, chief executive of the Law Society, said: ?We have serious concerns about the extension of powers for these case workers. Serious cases should be dealt with by properly qualified personnel who are fully responsible to the court.?

Sir Ken told The Times that most magistrates? cases were straightforward and involved fines, community penalties or discharges. ?I can well understand the sensitivities of the legal profession. This same trend is happening elsewhere ? nurses, for instance, are carrying out more procedures.?

He added that the case workers were high quality. They had often entered the CPS on law scholarships and then moved on to take degrees and become prosecutors. ?They will only do the level of case that I certify them for . . . and after appropriate training.?

Tom O?Sullivan, a public prosecutor and Law Society council member, has tabled a motion for the society?s council on Wednesday, opposing the plans. He said: ?The idea that regulated and highly trained solicitors can be replaced as prosecutors in summary trials runs contrary to the public interest and can only increase the likelihood of miscarriages of justice.?

Cindy Barnett, chairman of the Magistrates? Association, said: ?Magistrates deal with an enormous number of cases. We are most concerned that justice should be always be fair and efficient. Our priority is that every matter should be presented to us by those with sufficient training and expertise.?