A series of failures on a busy commuter rail line has caused misery for passengers with almost 6,400 minutes of delays in the last two weeks.

Network Rail admitted it was still not confident the problems on the Stratford to Snow Hill line have been fixed and business leaders called for more investment in infrastructure.

Since November 18 there have been seven days which have been hit with serious problems, including full shut downs of the track.

Operator London Midland revealed its services had been seriously hit by the problems which have been caused by signalling faults.

On November 18 the first shutdown hit and services were suspended. Train passengers had to put up with bus replacements for the next four days.

Despite extensive engineering work by Network Rail the next issue hit on November 21 during the evening peak. On November 30 the signalling again went down, then on December 1 there were no trains until the evening peak.

Again this week on December 2 the problem reoccurred.

London Midland revealed that so far the signalling problems had caused 6,341 minutes of delays for travellers.

224 trains were partly cancelled – they started their journeys but did not complete them and 41 never started.

Frustrated passengers took to Twitter to vent their anger.

Jo Owen said: "Shocking that @LondonMidland still unable to run a service on Stratford-Birmingham line 2 weeks after signalling problems started."

Ann Gallagher said: "My journey from yardley wood to snow hill - late yesterday - staff ??? Signals ??? Get it sorted !! This has been going on for a few days – cost me a fortune to get a relative from snow hill in taxi other day."

Andippe Purewal added: "@LondonMidland someone want to tell me why my train from langley has been canclled again making me late for college twice this week."

A spokesman for London Midland said: "While the impact has not been as bad as two weeks ago, we were disappointed when Network Rail reported further problems on the line. We are sorry to our passengers who have had to put up with still more disruption on the Snow Hill line.

"Regardless of the cause we want to apologise to our passengers for the inconvenience caused by the ongoing signalling problems."

John Lamb, from Birmingham Chambers of Commerce said the series of problems was an issue for businesses in the city.

He said: "Clearly there has been disruption to businesses which has been caused by this, with people arriving late for their jobs.

"I think that people who use the railways have become philosphical about things which go wrong, but what it does show is the desperate need for increased investment in the infrastructure to avoid issues like this."

A spokesman for Network Rail said: "Extensive testing of cables, circuits and equipment within a 15-mile stretch of railway has been taking place as we try to resolve an intermittent fault affecting signalling in the area.

"Testing continues as we do everything possible, with extra resource as well as external expertise, to identify the cause and make the repairs. This is an unusual situation and we apologise for the inconvenience caused.

"We are working with affected train operators to minimise disruption to passengers as much possible. Anyone planning to travel by train should check with National Rail Enquiries for the latest information."