The packages that were opened on Gibraltar's border with Spain were not diplomatic bags, Spain's Foreign Minister said.
Jose Garcia-Margallo reportedly told the BBC: "There is no incident. If it is not a diplomatic bag, there is no diplomatic incident. A bag was opened, which was not a diplomatic bag."
A Foreign Office spokesman said the bags were "clearly marked as the property of HM Government" and, as such, were covered by the Vienna Convention.
More top news
Two men seen as alternative voices to the US political establishment have won decisive victories in the New Hampshire presidential primary.
Takeaway food and alcohol are causing a growing obesity crisis among pets, according to a leading animal welfare charity.
Teacher shortages in England continue to grow and the government has missed recruitment targets, the National Audit Office says.