John Vine's inspection of e-Borders found that records relating to drug and tobacco smuggling were deleted over a 10-month period due to "poor data quality and the prioritisation of immigration over customs work".
The report said: "These deletions had a significant impact on the ability of staff at the border to seize prohibited and restricted goods and deal with those responsible."
It added: "This amounted to three quarters of all the customs work generated in NBTC and impacted on the ability of e-Borders to deliver anticipated benefits in relation to the seizure of prohibited and restricted goods."
More top news
High pressure in control over the next few days.