ALMOST half the £80million fleet of new trains introduced by First Great Eastern are today sitting in sidings.The fleet of 100mph "Desiro" electric units were introduced last year on the main line between Ipswich and London.

ALMOST half the £80million fleet of new trains introduced by First Great Eastern are today sitting in sidings.

The fleet of 100mph "Desiro" electric units were introduced last year on the main line between Ipswich and London.

But they have suffered serious teething troubles, and the decision to ground 10 of the 21-strong fleet with mechanical problems was taken this week.

And instead of enjoying the increased comfort of the modern units, passengers are now going back to the ageing slam-door trains that seemed to be a thing of the past.

Now engineers from Siemens, which built the units in Austria, are trying to find out the cause of the problems in the locomotives' transistors.

A spokeswoman for First Great Eastern reassured passengers they were not a risk in the Desiro trains still running.

She said: "There are no safety problems with these trains but the problem with the transistors does mean they are liable to break down regularly.

"Siemens' own engineers are now looking at what is the problem with them and hopefully these will all be sorted out soon."

When the trains were introduced during the summer they were heralded as a major improvement in passenger comfort on First Great Eastern's commuter services out of London.

They replace 27-year-old slam-door trains which have now been forced back into service while the new units are repaired.

Other services have been replaced by Anglia Railways' diesel units which have been hired in by First Great Eastern as they struggle to overcome their train shortage.