Temporary repairs were carried out in June, when the manufacturer CAF discovered cracks, but the operator, West Midlands Metro, said inspections have now found the cracks to be more extensive.
It said permanent repairs were now required and all services would be suspended.
The West Midlands Metro website says "We are sorry that there will be no Metro services from Saturday 13 November until further notice.
Earlier this year a repair programme was implemented to address cracks identified on several of our trams. As part of this work, it has become necessary for additional repairs to be carried out.
To ensure that we can continue to run a safe and reliable service, a decision has been made to remove all 21 trams from service until further notice.
This decision has not been taken lightly and we sincerely apologise for any inconvenience that may be caused.
Please be assured that every option has been fully considered to avoid suspending the service. As always, the safety of our customers and colleagues is our priority and this will never be compromised.
Your patience and understanding is very much appreciated while we work hard to resume services.
While this situation is ongoing, we are committed to keeping our customers moving. Metro tickets and passes will be valid on alternative modes of transport"
No Date has been given as to when services will resume, but repairs are expected to take at least four weeks.
West Midlands Metro said it was working with the manufacturer "to understand the issues and carry out the repairs as quickly as possible".
Eight million journeys were made on the network in 2019-20, according to figures from the Department for Transport.
As a stop gap, West Midlands Metro website displays a series of maps showing walking routes between tram stops here
Spanish rolling stock manufacturer CAF who supplied the the tram fleet, converted some of them to run on battery power in order to serve a recently introduced catenary-free section which runs through the centre of Birmingham.
A personal view from the Editor is now that battery power is a proven success there seems to be no reason ever again to erect new catenary which disfigures our streets.
If we take this one stage further, why disrupt people's lives by digging up roads and diverting underground services to lay tram tracks when guided bus schemes are in use and have been a success.
Previously, one of the selling points of trams was that they would last much longer in service than buses. West Midlands have already disposed of their original Ansaldo-Breda T-69 fleet, introduced in 1999 and replaced them with those that are already exhibiting structural faults.
Five year old tram tracks on Corporation Street in Birmingham have already been dug up and replaced at a cost of £5 million, so how can this all be justified?