Jubilee line is an Olympic concern this summer
Regular disruption on the Jubilee line is the biggest cause for concern for those looking into transport issues for this year's Olympics.
London Assembly's Transport Committee has written to the Mayor about the Tube link as it is the only line which has seen increased delays in the latest set of results.
It also raised concerns that it is yet to see the increased train number of 30 an hour promised to arrive this spring on the line which will serve Games venues at the O2 and Stratford this sumer.
Committee chair Caroline Pidgeon said: "Given the scale of the challenges, some disruption to the transport network is inevitable.
"Keeping the capital moving smoothly during the Games will be nothing short of a Herculean task."
The committee, which was running the report into transport progress in the run up to the Games, said in the main the outlook is good.
However, along with the Jubilee line, there was also worries over the Olympic Route Network confusing motorists and worsening traffic congestion and pollution.
"The amount of work that's going in to getting our already overburdened transport network ready to carry millions of extra athletes, officials and spectators is very impressive," said Ms Pidgeon.
"We are, however, keen to get some reassurance about the few areas - like the Jubilee line, local parking arrangements and the Olympic Route Network - that are still letting down what are otherwise very robust preparations."