British Transport Police's organisation is "impoverished and inadequate", HM Inspectorate of Constabulary has said.
Other than London Underground, operators were "loath to fund" BTP
With the sole exception of London Underground, train operators had been reluctant to fund the force to the required level, its report added.
Solutions to problems had been delayed and handling of calls was in "acute crisis", it claimed.
BTP Chief Constable Ian Johnston said: "At times we do struggle because of the lack of funding and people."
Theft of passengers' property had risen by 30% since the inspectorate's last report two-and-a-half years ago and the detection of such crimes stood at a "derisory" 2.5%.
The report said there had been little progress in crime management in three years but that the force had improved on other fronts.
BTP was praised for its record of solving the most serious crimes and the report said there was "professional competence and confidence" in the force.
But it said investigations into rail crashes were diluting the force's capacity.
The inspectorate also said there was scope to improve detection rates and called for a reinforcement of recent investment in forensic facilities.
Mr Johnston acknowledged the scope for "radical improvements" in the way BTP managed human resources, project management and business continuity plans.