The much-delayed upgrade of a busy Tube line is unlikely to be completed this year, leading to further service disruption, it has been announced.
The whole of the Jubilee line will have to close for one weekend in October, one weekend in November and over the Christmas period, London Underground (LU) said.
With only a “slim chance” of the upgrade being finished by the end of 2010, there will also be suspensions of service on part of the line during the autumn, LU added.
Sections of the Metropolitan Line will also be affected.
LU “inherited” the upgrade when it took over from Tube private maintenance company Tube Lines.
LU managing director Mike Brown said he wanted to apologise to “passengers, communities and businesses who have suffered years of closures”.
Brown added: “It is now clear that we inherited from Tube Lines a Jubilee Line upgrade programme which was badly behind schedule.
“When complete it will mean great improvements for passengers - with capacity boosted and journey times reduced, and we are now taking a major step forward by using the new signalling for the first time in passenger service.”