The use of sniffer dogs at Manchester Airport has been criticised after dogs there failed to discover any Class A drugs in a seven-month period.
But one dog, trained to detect illegal animal products, often found "small amounts of cheese or sausages" carried by holidaymakers, a report said.
The review, by the Independent Chief Inspector of Borders and Immigration, assessed border checks at the airport.
The Home Office said improvements "need to be made".
Other elements of border checks were also reviewed, with the report finding that:
- A "significant number" of Border Force staff at the airport were not fully trained in immigration work, leading to "delays and inefficiencies in the processing of passengers".
- Some staff were called upon to supervise immigration functions at a terminal for a shift "without the relevant immigration knowledge or training".
- There was a "control breach" in April 2015 when passengers from a delayed flight were "misdirected through an unmanned immigration control". Managers "acted decisively" to deal with the breach.
Some of the recommendations made had already been implemented, it added.
The report examined how "efficiently and effectively" Border Force - which is managed by the Home Office - operated at Manchester Airport.
The airport, the UK's third largest, has six detector dogs and new kennels, which cost £1.25m.
However, inspectors said that although heroin and cocaine were assessed as "very high priority" for the search team, no Class A drugs had been found by the dogs between November 2014 and June 2015.
One dog, which had been trained to sniff out smuggled animal products, had detected many items accurately - but the report said most were "small amounts of cheese or sausages, wrongly brought back by returning British holidaymakers and posing minimal risk to UK public health".
Inspectors said it would be of "more strategic value" to target flights where the dog might find bush-meat - which could pose a considerable threat to public health. A Home Office spokesman said inspectors recognised staff at the airport were conducting "all required checks at passport control".
"However, we acknowledge that further improvements need to be made. We welcome the report's findings and accept all the recommendations - many of which, including a new recruitment and training programme, are already being implemented," the spokesman added.