Numbers of staff at the Crown Prosecution Service who look after witnesses in court cases have more than halved in the last three years, it is reported.
Witness care staffing levels in England and Wales have been reduced by 57% since 2010, with a 24% cut in 2013 alone, from 131 staff to just 100.
As of January there were about 45 witness care units, compared with 80 in January 2012.
The findings were discovered by the Bureau of Investigative Journalism, in research carried out for The Independent.
The cuts have prompted fears that witnesses, many of whom may also be victims of crime, are receiving insufficient support before and during a court case.
The Crown Prosecution Service (CPS) claims cuts have involved the consolidation of witness care units, The Independent said, and that police have taken a larger role in supporting those giving evidence in court.
But policing numbers have fallen by 17% in England and Wales over the same period, the newspaper reported.
Witness care unit records show that the number of trials becoming ineffective because prosecution witnesses failed to attend has remained fairly constant, according to the Association of Chief Police Officers (Acpo) and the CPS.
A CPS spokesman said: "Conviction rates have remained consistent at 85% or above for the past eight years and the proportion of crown court trials ineffective due to prosecution reasons has fallen to 5% in 2013-14, the lowest level in four years."
However, figures from the Ministry of Justice (MoJ) show the staff cuts coincide with a small increase in the rate of crown court trials failing because of prosecution witnesses not attending, according to The Independent.
Some 16% of all ineffective crown court trials between January and September last year failed because of the absence of a prosecution witness, the newspaper claimed.
The Bureau also found that CPS legal teams, which prosecute suspected criminals, have faced a 31% cut in staff since 2010.
A study of 44 victims and witnesses from two English crown courts by the Institute for Criminal Policy Research also revealed many witnesses found their experience stressful, and that lengthy waiting times and inadequate information about when to attend court or that a trial had been postponed "exacerbated anxiety and inconvenience", The Independent said.
Labour's shadow attorney general Emily Thornberry told the newspaper she was concerned that the strain of government cuts to the CPS budget "is beginning to show on the ground", and has written to Attorney General Dominic Grieve to voice her concerns.
A CPS spokesman said: "We have had to make savings of 27% to our budget and naturally staff numbers have reduced, but we are protecting front-line teams and improving our overall performance."
Assistant Chief Constable Gary Cann, Acpo's national lead for victims and witnesses, said: "The police service is absolutely committed to providing victims and witnesses with the support they need to attend court.
"Over the last two years, we have refocused the work of the w itness care units to ensure that those victims and witnesses in greatest need, such as those who are vulnerable or intimidated, are given appropriate levels of support."