President George W. Bush lost one of his closest advisers on Friday when Dan Bartlett, the White House counsellor, announced his resignation.

As the president’s longest-serving aide, Mr Bartlett was one of the few remaining members of the close-knit group of Texan advisers that once formed the heart of the Bush administration. He is the latest in a series of high-level departures from the administration over the past 14 months as Mr Bush’s second-term agenda has slowed to a crawl amid turmoil in Iraq and the Democratic takeover of Capitol Hill.