Seventy percent of police officers say hand-held devices designed to cut time spent in the office have made them less efficient, according to a survey by the Scottish Police Federation.
In addition, 75% feel unsafe using the devices because of the concentration required to use them during "potentially confrontational situations".
Software problems with the devices have led to electronic notes being corrupted, forcing officers to re-enter information.
Of the 349 officers who trialled the personal digital assistants (PDAs), 70% said they made them less efficient, while 25% said there was no change. Just 10% said they were more efficient with the devices.
The Home Office has now spent £75m on the scheme. £50m was allocated in May this year, and a further £25m was announced in July. The funding will support the roll-out of 30,000 mobile devices. The plans were first announced in September 2007.
PDAs are intended to reduce the amount of time officers spend filling in paperwork at the office, and increase the amount of time they spend on patrol. Police enter information into the system on the street, instead of going back to the office to use a computer.
A report by the Home Affairs Select Committee showed not all officers are convinced of the benefits of PDAs.
But Inspector Jim Hitch of Bedfordshire Police, which worked with the National Police Improvement Agency (NPIA) in trialling the devices, said they had reduced the amount of time police officers spent in the office from 46% to 36%, and visible patrol time rose from 14% to 19% during trials.
Ian Johnston, chief constable of the British Transport Police, told the committee that while officers had concerns about using PDAs, he expected them to become more comfortable with them over time.
The Police Federation said greater consideration of end-users' views on what is workable in system design and implementation is needed.
Despite officers' misgivings, the Committee recommended that funding is made available for all police to have PDAs.