The man who holds Britain's border controls to account has announced plans to resign earlier than planned.
John Vine, chief inspector of borders and immigration, will step down on 31 December - seven months earlier than originally planned.
Mr Vine has published more than 50 inspection reports during his near six-year tenure, including findings that exposed huge backlogs in the now-defunct UK Border Agency.
Announcing his decision to resign, Mr Vine said: "I am immensely proud of establishing this Inspectorate from scratch, and believe it has been a catalyst for significant change and improvement across the UK's border and immigration functions.
"After publishing over 50 inspection reports and making close to 500 recommendations, the time is right for me to seek a new challenge."
The chief inspector denied he was stepping down after becoming frustrated with a change in the publication process for his reports.
"I have raised my concerns with the change in publication processes with the Home Secretary and the Home Affairs Committee previously, but this is not the reason I have decided to resign," he said.
Mr Vine was due to step down at the end of his current term in July 2015.
David Hanson, shadow immigration minister, said: "John Vine's departure is an indictment of Theresa May's attempts to silence his criticisms of her failing immigration system.
"I'm sad to hear of John's departure - he did a superb job as Chief Inspector and brought a rigorous and determined approach to the role of scrutinising our borders, his reports highlighted flaws in the Home Secretary's immigration regime and instead of rectifying them she sought to increasingly hold back his recommendations."