The Army is investigating claims that soldiers from Princes William and Harry’s former regiment – including a female trooper previously disciplined over claims she sexually assaulted a male colleague – took hallucinogenic Class A drugs.

The squaddies, from the prestigious Household Cavalry based near Windsor Castle, are being probed by Royal Military Police officers and are undergoing compulsory drugs tests which could lead to their dismissal from the ranks.

The Mail on Sunday has been told how Trooper Corrie-Alice Holmes has apparently admitted taking ecstasy, also known as MDMA, while male troops being investigated deny drug-taking.

Under investigation: Trooper Corrie-Alice Holmes has apparently admitted to drug use

Earlier this year Tpr Holmes, 25, was warned about her conduct after allegations surfaced that she allegedly ‘molested’ a male colleague after returning to the barracks. She had been drinking heavily in bars near the base.

Tpr Holmes was said to have forced herself against the younger soldier, tried to kiss him and rubbed her body against his, before being pulled off by a furious officer who reacted to the male soldier’s cries for help.

The following day, Tpr Holmes was hauled before senior officers who formally warned her that any further misconduct could result in her being immediately dismissed from the Army.

But the second chance given to Tpr Holmes by regimental commanders aggrieved some male soldiers in her unit. They suggested that had they assaulted one of their female colleagues, they would have been booted out straight away.

The Mail on Sunday has reported cases of male troops being sent to military prison and being dismissed from military service at the end of their sentences for behaviour similar to that of Tpr Holmes.

Last night, defence sources suggested that male Household Cavalry troops were leaking information about Tpr Holmes to the media because they bear a grudge against her. Sources added that since being warned by commanders in January, she had performed well. One source said: ‘She has been a highly professional soldier since then and I think some people still have it in for her. Her confession and the claims that other personnel took MDMA are now under investigation and members of the Household Cavalry are being drug tested.

‘Would this sort of information be getting out if a male soldier had misbehaved? There could be a witch-hunt going on, which is a great shame because Tpr Holmes has many redeeming qualities.’

An Army spokesperson said: ‘We have a zero-tolerance drugs policy. Any personnel caught taking drugs will be discharged.’