Line part suspended throughout rush hour in what unions say has been a 'week of chaos' on the Underground

There was fresh misery for commuters on the London Underground this morning as parts of the Jubilee line were suspended throughout rush hour because of a cracked rail.

Continuing what unions have described as "week of chaos" on the tube, the line, which is used by more than 500,000 passengers a day, remained partially closed this lunchtime, resulting in packed trains elsewhere on the network and delays to many workers in the capital.

The disruption came after thousands of passengers had to walk along tracks through darkened tunnels due to a power failure and a defective train on consecutive days earlier this week, forcing a public apology from Mike Brown, London Underground's managing director.

Unions today pointed to cuts in maintenance and a partly privatised upgrade to the Jubilee line and pledged to press ahead next month with planned strikes against job cuts that they claim would "plunge travellers even deeper into the black hole of unsafe and unreliable services".

The Jubilee line was closed between Waterloo and Green Park during rush hour this morning – a suspension that was later extended to cover all stations between Waterloo and Finchley Road.

Commuters on the Jubilee line were forced to walk along tunnels following a power failure during rush hour on Monday. On Tuesday, 400 commuters on the Victoria line had to be led to safety from a defective train.

Acknowledging that this would have been a "distressing" experience for many, Brown said on Tuesday: "Our customers deserve much better than the service they have had in recent days and all our energies are focused on delivering a fast, reliable and safe service."

There could be further widespread disruption on the tube next month, with members of the Rail Maritime and Transport Union and Transport Salaried Staffs Association planning two days of strike action in protest against what they claim are plans by Transport for London to cut 2,000 jobs.

Bob Crow, the general secretary of the RMT union, said: "Once again this morning the transport system in London has been reduced to chaos with a cracked rail on the Jubilee line – a line that has cost billions in upgrading through the privatised PPP (public private partnership) and where we have ended up with an operating system that doesn't operate and is prone to the kind of frequent breakdowns that have hit thousands of passengers this week.

"On top of that we have a combination of reductions in maintenance, financial cuts and a withdrawal of goodwill by tube staff who are furious at the ongoing threat to another 2,000 jobs."

London Underground said: "The Jubilee line is currently suspended between Finchley Road and Waterloo due to emergency engineering work in the Green Park area. A cracked rail was identified during our routine maintenance check and we are working to rectify the problem as quickly as possible, we apologise for the inconvenience caused."