There has been more morning misery for Tube travellers following a series of rush-hour problems.

The Jubilee line was part-suspended due to a signal failure at Stanmore, with Metropolitan line trains also held up in the Finchley Road and Baker Street areas.

Another signalling problem, at Caledonian Road, led to delays on the Piccadilly line, while there were severe delays on the Bakerloo line due to a faulty train at Piccadilly Circus.

It was the latest in a string of morning disruptions on the London Underground which will be launching all-night services in September.

Mick Cash, general secretary of the RMT transport union, said: "The engineering and fleet issues that have arisen yet again on this Monday morning are a massive reminder of just how challenging the environment is for the teams of staff out there day and night keeping London moving.

"Those challenges will be ratcheted up by the plans for night running, plans that the politicians say they now want to extend across the system and on to London Overground."

London Underground's chief operating officer, Nick Brown, said, "I apologise to customers for the disruption they've suffered this morning on some Tube lines due to problems including signal failures and faulty trains.

"Our engineers are working as quickly as possible to restore services on the affected lines. We will be refunding customers who were affected by the disrupted services this morning."