The backlog of 153,000 notifications could potentially have meant that thousands were wrongly allowed to remain in the country, the Chief Inspector of Borders and Immigration said.
The tip-offs were all reviewed by May this year, but Mr Vine said it must be an "ongoing priority" to make sure checks are carried out.
His team examined work at three UKBA offices in Sheffield, Beijing and Delhi.
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A remarkably mild night with misty low cloud on the hills of Scotland, Wales and north-west England and further rain in places.
There's a wider purpose to Prince Charles' nine-day visit to Romania, Italy, Austria today.
A man and a woman, both in their early 20s, have been arrested in Birmingham on suspicion of terrorism offences.