Some emerged vomiting from the vehicles, while others were shaking after the military exercise on Salisbury Plain, in Wiltshire, according toThe Times, external newspaper.

It comes just weeks after the UK government said it was "confident" Nato allies would beinterested in buying the armoured vehicles that were made in south Wales.

• Nato interest in 'lethal' Army vehicle, says minister

  Published
  6 November

• Systemic failures found in Army vehicle review

  Published
  16 June 2023

Defence minister Luke Pollard claimed the £6.3bn programme had "left its troubles behind", as Ajax declared initial operating capability (IOC), which means it can deploy a squadron on operations.

The multi-million pound vehicles, made in Merthyr Tydfil by General Dynamics, were originally due to enter service in 2019.

"This weekend, a small number of soldiers reported symptoms of noise and vibration, having taken part in an exercise involving the Ajax armoured fighting vehicle," an MoD spokesperson said.

Upon testing "around 30 personnel presented noise and vibration symptoms".

A "small number of personnel" are still receiving expert medical care, it added, but the "vast majority" have been cleared for duty.

"Out of an abundance of caution, the minister for defence readiness and industry has asked the Army to pause all use of Ajax for training and exercising for two weeks, while a safety investigation is carried out into the events this weekend.

"A small amount of testing of the vehicle will continue, in order to ensure that any issues can to identified and resolved."

The Ajax programme has suffered long delays because noise and vibration have injured soldiers who have tested the vehicles.

A review of the £6.3bn programme in 2023 highlighted"systemic, cultural and institutional problems" at the MoD and a "a number of errors of judgement" in the Ajax project.

More than 160 Ajax vehicles have been built, out of an intended 589.

Before the two-week pause was declared, it had been estimated that full operating capacity for the programme may not be achieved for another four years.

Speaking on 5 November, Pollard said the Ajax vehicles had proved to be the "most advanced medium-weight armoured fighting vehicle on the planet".

"We have more than a full squadron ready to go, ready to fight, ready to win, with more in the pipeline," he added.

Ajax is a replacement for the aging fleet of CVR(T) vehicles which first entered service in 1971.

By Jonathan Beale, Defence correspondent

The Ajax armoured vehicle has long been referred to as a "troubled programme" - plagued by delays and technical faults.

The British Army ordered the vehicle in 2014. It was supposed to be fully in service by now. But it's not.

Problems with excessive noise and vibration were said to have been resolved years ago.

In 2023, then Defence Secretary Ben Wallace said Ajax had finally "turned the corner". There are clearly still problems.

The Ministry of Defence often rejects allegations of being involved in a long list of procurement errors. But that's getting harder to deny with Ajax.

A failed attempt to hide some of the projects problems hasn't helped either.