The Ministry of Defence has spent £149m on an urgent "upgrade" to 900 tanks that are only now being used in training exercises, it has been revealed.
The vehicles, originally ordered for Iraq, are unsuitable for use in Afghanistan. The upgrade programme was ordered three years ago as an "urgent operational requirement".
It saw 900 of the FV430-variant armoured units refitted with new engines, drive trains and driver controls.
A spokesman for the Ministry of Defence said: "We provide our armed forces with the vehicles that best meet their operational need. The Bulldog was specifically upgraded for use in Iraq where it played a key role in providing armoured protection for many personnel.
"In Afghanistan, where the terrain and threats are different, this role is performed by the Mastiff and Ridgback. The Bulldogs continue to have a role in training exercises in the UK."
The shadow defence secretary, Liam Fox, said: "We are increasingly concerned that the procurement programme is out of tandem with our military needs. This needs to be done on a detailed and thoughtful basis which can only come as part of major acquisition reform."
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