CNN is preparing to make substantial cuts to its London-based television news operation in a move that is likely to result in at least a dozen employees losing their jobs.

The announcement was made by Jeff Zucker, the CNN boss, at a “town hall” meeting on Tuesday in the company’s office in central London.

Staff, including some managers whose shows were affected, were given no advance warning of the announcement, according to some of those present. Zucker told them that the international channel was losing $10m (£8m) a year, according to those present.

The cuts come shortly after the longstanding CNN International boss Tony Maddox unexpectedly announced he was leaving the station earlier this month.

Viewers of CNN International will see less material produced in London in the short term, with the total amount to be cut by 90 minutes a day.

The channel, aimed at a global audience, will instead show more simulcasts of the main US CNN network, extra repeats of the flagship Christiane Amanpour programme and additional programming produced out of CNN’s Abu Dhabi office, according to staff at the meeting.

London-based shows such as the discussion programme CNN Talk will be cut completely as the company focuses its British office on its online offering at the expense of its traditional TV channels.

CNN has found itself at the heart of a battle between Donald Trump and the media, with the channel being labelled “fake news” by the US president in press conferences.

The broadcaster’s parent company Time Warner, which also owns the Warner Bros movie studio and the Game of Thrones producer HBO, was recently bought by the US cable company AT&T. The purchase of the business, renamed WarnerMedia, has prompted a reappraisal of CNN, including changes to its CNN Vision production business.

Although most London-based roles are being relocated to Atlanta, New York and Abu Dhabi, many British staff are not expecting to be able to take up the jobs. Some hope to make the move, but have been warned that they would not automatically be considered for the relocated roles, with their associated visa issues. Thirteen roles have been confirmed as being affected by the changes.

Zucker said he would protect the digital and newsgathering operations, with the cuts likely to hit the teams that produce live TV programmes and work on individual shows.

A spokesperson for the channel said: “In the coming months, CNN International will be consolidating key parts of its production model centrally in Atlanta, in much the same way as we currently do with large parts of our programming for CNN US. This means that some jobs will shift from London to Atlanta, but overall headcount will be unchanged.”