Maintenance staff on three tube lines are entering their third day of strikes today.
A strike affecting the Jubilee, Northern and Piccadilly lines goes ahead from 4pm.
Union bosses have forecast "widespread" disruption, as workers who maintain and upgrade tube lines go on strike next week.
The RMT union has claimed that South West Trains has broken an agreement that the company would operate "as usual" during the Olympics and Paralympics. The union says SWT is advertising additional trains and later running services over the entire period and has called a ballot for industral action.
– Bob Crow, RMT General Secretary
"Other train operators, notably Heathrow Express this week, have negotiated agreements with RMT that recognise the added pressures of the Olympics. South West Trains have taken a different approach... trying to bully staff into accepting enforced increases to working hours and workload with nothing in return."
The RMT union has said it is balloting cleaners who clean the London Underground for strike action. The union says the cleaners, who work for the companies ISS and Initial, deserve a substantial pay increase as well as other benefits.
A little over two hours ago tube maintenance workers walked out, starting a 3 day strike over pensions and benefits.
The question is, will anyone notice?
The RMT says service will be affected. TFL says there won't be a major impact.
Our business correspondent, Glen Goodman, spoke to Jon Lamonte from Transport for London, and sent this report from RMT Headquarters.
At 4pm, maintenance workers on three Tube lines will go on strike in a row over pensions and conditions. Daisy Gray reports.
Jon Lamonte of Tube Lines says they have prepared contingency plans to keep the Underground moving during the strike. Some maintenance workers will walk out at 4pm this afternoon.
London Underground has denied it will bring back Public Private Partnership schemes on the network. The RMT union claimed the current row over Tube Lines pensions indicated LU wanted to bring in private firms. But LU's managing director Mike Brown said it intended to keep control of Tube projects.
– Mike Brown, London Underground
"There are no plans to repeat the PPP structures of the past. LU has recently taken the maintenance of the Jubilee fleet of trains back under our direct control. Our actions speak for themselves."
The RMT union has launched a defamation action against Boris Johnson. It claims that his campaign posters portrayed the union's General Secretary Bob Crow as "being part of a culture of political immorality and as having caused serious harm to the interests of people in London".
– RMT trade union
We are prepared to engage in meaningful negotiations but Tube Lines are not, as they made clear at ACAS yesterday. They wouldn’t move their position at all, effectively collapsing the talks right from the start.