Linda Lees, 45, appeared for sentence at Truro Crown Court having pleaded guilty at an earlier hearing to three charges of administering to her husband Paul a poisonous, noxious or destructive substance.

Lees, from Helston, Cornwall, was given a 49-week prison sentence, suspended for 18 months, and ordered to pay £300 costs.

Judge Christopher Elwen ordered her not to visit her husband's home in Southsea, or his place of work, and not to contact him except through her solicitor.

Mr Lees was a Chief Petty Officer in the Royal Navy and is now an avionics instructor at HMS Sultan, Portsmouth.

Prosecutor Philip Lee said Lees and her husband had been living separate lives, and last October he told her he felt they should divorce.

He had formed a relationship with a woman he had met in the United States - and when Lees found out in January she was unhappy about it.

Lees was twice taken to hospital in March after taking paracetamol and temazepam.

The prosecutor said Mr Lees stayed with his wife and their daughter at Easter; they had a takeaway meal and he remembered the wine tasting salty.

"He went to the bathroom feeling groggy and weak, she pushed him and he fell down the stairs.

"Lees called the police, and her husband told them he had been drunk and no action was taken," said the prosecutor.

Lees and her husband later had a meal together in Exeter, where he joked about her drugging him.

"He did consume something which made him feel groggy afterwards. It was not as bad as previously and he drove back to Portsmouth," said Mr Lee.

In July there was a further meeting to discuss finances and for Mr Lees to collect property from the matrimonial home.

"Again they had a takeaway and watched television and his next recollection was of being taken to her car and driven around the area, and then of coming to in the garage with the door shut," said Mr Lee.

"He saw a hosepipe leading in through a window. He remembers being on a stretcher and taken to hospital.

"Again it became clear he had been drugged and there was evidence of temazepam .

"His wife was found in the garage. The car engine was not running but there was a pipe leading in through the window."

Mr Lee said that when Lees was interviewed she admitted she had put temazepam into her husband's drink, adding: "I wanted him to be asleep while I did this. I did not want him to stop me."

The amount of temazepam taken was not a fatal dose, said the prosecutor.

She agreed she had tried to commit suicide and that she had drugged her husband three times with her prescribed drugs.

Terry Eastwood, defending, said that Lees had given her husband temazepam to enable her to gain access to his mobile phone and information about an affair she suspected he was having with an American woman.

In July she had wanted to stupefy him and make sure he was asleep while she committed suicide. She had never intended to kill him.

Mr Eastwood said Lees, who married her husband in 1986, had been on "an emotional roller coaster".

The judge told Lees she had on several occasions by her own admissions administered the anti-depressant temazepam in various doses to her husband without his knowledge.

"The offences were all planned and the outcome on each occasion could have been much more serious than it was.

"The Crown has accepted it was not your intention to kill your husband but the outcome could have been dire," said the judge.