The Guardian newspaper will soon abandon its European-style “Berliner” print format and go tabloid to help stem heavy losses.

It is understood that an agreement to outsource printing to Trinity Mirror could be announced as soon as this week, although senior sources said it was not yet completely finalised. The plans mean The Guardian will be redesigned to fit smaller tabloid pages.

A source close to the negotiations said: "This deal makes great sense to the Guardian financially.

"It keeps the journalism available in print, which many readers really value, and it will offer much more flexibility for the future."

The contract will also allow the newspaper to scrap or sell its three Berliner presses, which cost £50m in 2005. It spent a further £30m on printworks in London and Manchester.

The Guardian was the first and only major UK title to adopt the Berliner format, which is taller than tabloid and narrower than a broadsheet.

At the time The Guardian said the investment would give readers "the best of both worlds", offering "broadsheet values" and the convenience of a smaller newspaper. It said it had decided to "avoid the ‘easy’ short-term tabloid route".

The presses have spent an increasing proportion of time idle as readers have migrated online, however. The Guardian’s average circulation in April was 154,000, compared with 341,000 in the same month in 2005.