A Royal Navy lieutenant sexually assaulted a female colleague in front of young sea cadets during a tour of a nuclear submarine.

Lieutenant Basil Purdue, 26, was found guilty at a court martial trial at Portsmouth Naval Base of groping her breast over her clothing.

She was helping him show the youngsters around HMS Vanguard at the Trident submarine base in Helensburgh, Argyll, in February last year.

He then aimed a sexually explicit comment at his victim, who cannot be named for legal reasons.

A panel of senior officers sentenced Purdue, a submariner, to a three-month prison sentence suspended for two years, dismissal with disgrace from the service, the payment of £750 compensation to the victim and to sign the sex offenders register for seven years.

Judge advocate Robert Hill said: "This was a sexual assault by an officer in circumstances where there was an element of bullying by saying you could get away with it because of your rank.

"This has affected her significantly. She was already miserable because of the sexualised banter of those of her own rank.

"You have gone in and calmed that down for her, that doesn't sit well with what happened on the day in question. This was a gross dereliction of duty to behave in this way."

Captain Alison Towler, prosecuting, told the court the victim had been left "humiliated and ashamed" by the assault and questioning her career in the navy because she had lost her trust in men.

Reading from the victim's impact statement, she said: "I have become frustrated and angry and do not know where to turn.

"I feel like I am falling into vicious circle of being angry and sad and feel like I need to lash out. I wonder if the Royal Navy is for me I am wondering if this could happen again.

"I have constantly battled to argue that women are equal in the Royal Navy but now I feel they are not."

Damian Hayes, defending, said Purdue, who had been in the navy for seven years, continued to deny the offence and said the conviction had destroyed his reputation as a man of "integrity, trustworthiness, support of others, Christian faith and positive attitude to life".

He added Purdue, based at HMS Excellent, Portsmouth, had been supported throughout the trial by his parents and his wife, Helen, who had written a letter to the court describing the "happiness and strength of their marriage".

Mr Hayes said: "He has lost his good name and his good reputation and for the foreseeable future he will have to sign on as a sex offender, which is an everyday reminder of his shame."