Michael Crick, Channel 4 News’s political correspondent since 2011, has abruptly parted company with the broadcaster.

He tweeted on Wednesday: “I have left Channel 4 News and ITN after seven and a half great years. Farewell to all my fabulous colleagues. I’m looking forward to an exciting new life writing books again, and all sorts of other activity in journalism and other fields.”

Channel 4 News would not comment on the reasons for Crick’s unexpected departure. A spokesperson said: “He has set out his position in his tweet.”

Multiple sources at the programme said they had no inkling that the prominent reporter was about to depart until an email from the Channel 4 News editor, Ben de Pear, was sent to staff on Wednesday.

“This is to let you all know that Michael Crick has left Channel 4 News after seven years,” wrote de Pear. “One of Britain’s most experienced and decorated TV news correspondents, his latest spell with the programme coincides with the busiest period in recent political history and he was recognised as specialist journalist of the year twice at the RTS journalism awards within five years.

“In 2018 Michael won the prestigious Charles Wheeler award for excellence in broadcasting for his forensic investigative skills and obsessive eye for detail. His relentless drive has resulted in a string of scoops including most recently the election expenses scandal and changing the very nature of the coverage of the 2017 election campaign. His pursuit of politicians resulted in some of the most memorable and longest doorsteps in television news history.

“Michael now plans to get back to writing books, and to pursue other forms of journalism as a freelance.”

The 60-year-old reporter was in his second stint at Channel 4 News, having been part of the team which launched the programme in November 1982.

He was the channel’s Washington correspondent between 1988 and 1990, after which he joined the BBC, where he worked first on Panorama and then on Newsnight, eventually becoming political editor in 2007.

He rejoined Channel 4 in 2011, where he was given free rein to pursue niche political stories and was known for his energetic chasing of politicians. He was once hit over the head by the Ukip MEP Godfrey Bloom, who also suggested that he wanted to shoot the journalist.

Crick led the way on Channel 4’s investigation into Conservative election expenses, which ultimately resulted in the conviction of a long-standing Conservative aide – although the Conservative MP Craig Mackinlay was acquitted in January this year.

After leaving Oxford University in 1980, Crick was offered the chance to contest the safe Labour seat of Bootle in Merseyside, but turned the offer down. Outside politics, he is a supporter of Manchester United, and wrote a biography of the former manager Sir Alex Ferguson in 2002.