Scotland's prosecution service needs to "significantly up its game" to support victims and witnesses as cases go to court, it has been claimed.

The Scottish Police Federation (SPF), which represents rank and file officers, said courts faced an "unrealistic" volume of cases which put staff under considerable pressure.

The body criticised "farcical levels of disturbance and inconvenience" in the prosecution system.

Holyrood's justice committee is carrying out an inquiry into the role and purpose of the Crown Office and Procurator Fiscal Service (COPFS).

It is due to hear from SPF's general secretary Calum Steele on Tuesday.

In a written submission to the committee, he praised the "dedicated, professional and incredibly hard-working" staff working in the prosecution service.

But he added: "It is the experience of our members that when matters get to court, the procurators fiscal are often unprepared and lack knowledge of the case."

The SPF said engagement with prosecutors on complex and serious cases was usually "second to none" but raised concerns that the COPFS "does not have the skill set to carry out its role effectively" in cases involving new technologies.

Mr Steele's submission states: "The SPF believes that the COPFS needs to significantly 'up its game' in both its dealing with victims and witnesses.

"This is especially true when it comes to the court experience where what can only be described as farcical levels of disturbance and inconvenience are experienced.

"We appreciate that court scheduling is a matter not directly in the hands of the COPFS but the volume of cases that can be laid down for a particular court hearing are by any measure unrealistic.

"It appears to the SPF that large numbers of cases are called, not because there is any prospect of the case being heard, but to ensure timescales can be adhered to."

The federation said the frequency of cases being adjourned or abandoned was too high.

"In many cases these adjournments and abandonments see victims lose confidence in the justice system and witnesses increasingly frustrated at having to waste their days lolling around court corridors," Mr Steele wrote.

The SPF also raised concerns that cases were proceeding despite a lack of evidence to secure a conviction, particularly in relation to domestic violence.

In a separate submission, the Faculty of Advocates said it believed "that a lack of resources within COPFS has had a significant impact on the effectiveness and efficiency of the pre-indictment preparation of non-homicide and non-sexual cases".

It also noted a "general deterioration" in the standard of preparation leading up to an indictment in non-homicide and non-sexual offence cases.

It added: "The Faculty questions whether COPFS has the resources and expertise to prepare and present the prosecution of other complex cases."

A Crown Office spokesman said: "We strongly disagree with many of their conclusions, but we appreciate that the SPF has recognised our staff to be dedicated, professional and incredibly hard-working.

"We have set up specialist units within COPFS to ensure that we are well equipped to deal with the latest threats facing the public, and remain one step ahead of those who commit crime, applying a consistent approach to prosecution policy across the country.

"Victims are at the heart of the justice system and we are absolutely committed to ensuring that their interests are well served.

"We are working with criminal justice partners to minimise inconvenience to both witnesses and victims of crime, and we can assure the federation that we only take action in cases reported by the police where we consider there is sufficient evidence in law.

"Giving evidence is a core part of police officers' duties and not all citations will result in officers and other witnesses having to attend court; a number of citations are cancelled before the trial date if the accused pleads guilty at an earlier stage in proceedings."