National Highways senior project manager Jonathan Wade said: "Periods of extreme weather in 2024 delayed some elements of our work but since then we've worked hard to recoup that time and still complete the on-road elements on schedule.
Steve Gooding, director of motoring research charity the RAC Foundation, said: "Motorists who've grown used to the queues and closures associated with this scheme must now brace themselves for another summer, autumn and winter of discontent as the completion of work slips into 2026.".
But Mr Wade said it was the “final block of closures” on the M25 and urged motorists to rely on official diversion routes rather than sat-nav routes through minor roads.
The motorway will be closed between Junctions 10 and 11 from 9pm on Friday March 7 and 6am on Monday March 10, and over the same period a fortnight later.
It means a stretch of the motorway will be fully or partially-closed again on two full weekends in March, National Highways said.
