A woman who moved to West Yorkshire to continue an affair with a married man was behind bars today after she hired a hitman to kill his wife.

A Court heard that the man Hayley Johnston asked to carry out the killing for £10,000 was an undercover detective.

"Obsessed" Johnston, 43, of Malham Road, Brighouse, was yesterday jailed for five and a half years after she pleaded guilty to soliciting a murder.

Judge Clement Goldstone told her: "This was no harebrained scheme in which your mind was overborne by fantasy. This was a determined effort by you.

"You were motivated by two factors. Firstly, obsession with a man who had an unhealthy influence on your life, and secondly, hatred for his wife."

Prosecutor Rachel Smith told Manchester Crown Court that Johnston began an affair with Stuart Johnston when they were both married and living in Surrey in 1997. Mr Johnston's wife Rosalynd discovered the affair and the family tried to start afresh by moving to Wakefield in 2001.

But Hayley Johnston also moved to the area and the affair continued. The court heard Stuart Johnston could not choose between the two women and spent time living with the defendant but in February 2003 returned to his wife and their two children, now aged 12 and 13.

His jilted mistress was furious and began plotting to win him back by having his wife murdered. There was no suggestion that Mr Johnston knew about the plot or played any part in it.

Hayley Johnston, who worked at a Leeds cleaning firm, was interviewing a former prisoner for a job when she asked if he knew any hitmen. He contacted police and then co-operated with them to introduce her to "Mac", the undercover officer.

The court watched a secretly-filmed video of Mac meeting the defendant at a service station near Leeds. Asked how she wanted the murder carried out, she said: "I don't care. I just want her six feet under."

In mitigation, Kate Blackwell said Johnston had been "besotted" by Stuart Johnston, who damaged her self-esteem by using her financially and refusing to make a clean break of their affair. She added that it was his suggestion that she change her name to Johnston, so they would be more like man and wife.

After yesterday's court hearing, Rosalynd Johnston said: "Since the police came to tell me what they had uncovered it has been a living hell. I still can't believe she thought she could get away with it. The thought she wanted to have me killed and leave my children without their mother is terrifying."

Detective Inspector Bill Beddows, of Greater Manchester Police, said Johnston was a very dangerous woman who had made a calculated attempt to commit murder.