THE London Underground boss has apologised for chaos on the Victoria Line and blasted contractors over the disruption.

Problems with an upgrade to the signalling system at Seven Sisters installed during weekend engineering work spread more misery for passengers who have grown used to closures.

Trains were not running between Highbury and Islington and Seven Sisters last night and there were delays on the rest of the line.

Mike Brown, London Underground's managing director, said yesterday: “I apologise to passengers for the disruption on the Victoria Line today and assure them that we are doing everything possible to resolve the issue and minimise the disruption as they travel home.

“I'm very disappointed that our contractors have failed today to deliver the reliable service that our passengers deserve, and we are pressing both Invensys and Bombardier to take every measure to ensure this situation is not repeated.”

The chaos followed a signal failure at Seven Sisters and engineers were working “flat out” to repair the problem, Transport for London (TfL) said.

Victoria Line passengers who used Oyster pay-as-you go during the disruption will be automatically refunded while anyone with a paper ticket can apply for their money back.

TfL said the upgrade, once fully operational, will increase capacity by 21 per cent allowing 10,000 extra journeys per hour.