The number of inspections, which are handled by local authorities, fell from 307,526 in 2003-04 to 260,765 in 2014-15, the study found.
The Food Standards Agency watchdog said the situation was of “growing concern”.
The Local Government Association said councils “work extremely hard” on food safety despite budgetary pressures.
Ministers said public safety was “paramount” and the “majority of local authorities have continued to balance their budgets and increased or maintained public satisfaction with services”.
The figures, obtained by Prof Steve Tombs for the Centre for Crime and Justice Studies, using freedom of information requests to the Food Standards Agency (FSA), show almost 47,000 fewer inspections were carried out in 2014 than in 2003.
The number of establishments prosecuted also fell by 35%, from 552 to 361, over the same period.
Prof Tombs, who is professor of criminology at the Open University, said “policymakers need to urgently address the radical reduction in local authority inspections and enforcement.”
The BBC’s 5 live Investigates programme has seen minutes of an FSA board meeting from January this year where concerns were raised over rising numbers of complaints and falling staffing levels.
“The overall position is one of growing concern,” the agency warned.
“At a local level, there are a good number of authorities which are struggling to undertake interventions of food businesses at the required frequencies.”
The minutes also state that many local authorities “are not able to deliver a food service as set out in statutory Food Law Code of Practice”.
Debby’s 10-year-old daughter was admitted to hospital during a salmonella outbreak in 2014 which affected 54 people.
“She started complaining of severe stomach cramps. She had really bad diarrhea and she was having bad hallucinations.”
Investigators found poor hygiene procedures at a takeaway, which cannot be named for legal reasons, allowed potentially deadly salmonella bacteria to pass from eggs to other food.
The last full inspection of the premises was 20 months before the outbreak and it received a Food Hygiene Rating of two, which means that “improvement is necessary”.
In June 2013 an environmental health officer visited to provide “support and guidance”- and a year later the outbreak occurred.
“If I’d known that I would have kept away and we never would have bought anything from there,” said Debby, who does not want to use her full name.
The local authority involved said it visited in 2013 and “was confident that improvements were being made. A further inspection was imminent, as part of routine procedures, when the council received notification of the reported links to salmonella cases.”
