Trials of a new £3.47bn fleet of army tanks have been paused over speed and safety concerns, the Ministry of Defence has confirmed.
The armoured fighting vehicles have design issues which reportedly include them being unable to travel safely faster than 20mph – and they are supposed to be able to go up to 40mph.
Other problems with the new Ajax armoured range include an inability to fire cannons on the move, according to The Daily Telegraph.
Citing a government report, the newspaper said the speed restrictions had been caused by excessive vibrations in the tanks, adding that crews were limited to 90 minutes inside them at a time.
The report, due to be published next month, also says the tanks cannot reverse over obstacles more than 20cm high.
It also claims that personnel must wear noise-cancelling headphones when operating the tanks and have to undergo ear tests afterwards.
The Household Cavalry Regiment "cannot conduct effective collective training" in them, the report adds.
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The MoD introduced the new range of tanks in 2010, with 589 vehicles across a range of models ordered in 2014.
But the programme has had a slew of problems and is four years behind schedule, the Telegraph reported.
The paper added that only 14 of the turretless Ares model tanks, made by US firm General Dynamics, had been delivered.
In a statement, the MoD said its training on "Ajax variants" had now restarted "with appropriate safety measures in place".
An MoD spokesman said in a statement: "We are committed to the Ajax programme which will form a key component in the Army's modernised warfighting division, with current plans for Initial Operating Capability scheduled for summer 2021," an MOD Spokesperson said in a statement.
"The MOD can confirm that some training on the Ajax family of vehicles was paused as a precautionary measure.
"This is a normal measure for the demonstration phase of projects; an investigation, incorporating trials, is being carried out jointly with the manufacturer. It is inappropriate for us to comment further at this time.
"The health and safety of our personnel is of the utmost importance and we are committed to providing a safe working environment."