A Border Force spokesman said:
"Border Force and BAA data shows that queuing time targets for UK and EEA citizens were not breached during April.
"But we know at times queues have been too long.
"That is why we have announced an extra 80 staff for peak times at Heathrow. And it's why we've also engaged an extra 480 people to cover the Olympic period.
"In the longer term, our management and rostering changes will address the issue of queues."
Immigration Minister Damian Green has previously said that last week's problems at Heathrow were mainly due to poor weather - and that it is essential that the UK's borders are secure.
He has also said that all immigration desks at key ports and airports will be fully staffed during peak periods throughout the Olympics.