An “obsessed” son has been jailed for sending countless poison pen letters to his elderly mum and her boyfriend in a bid to split them up.

Joseph Carson sent letters and texts to his 80-year-old mother Jane, her former boyfriend Ronald Moreland, 77, and their friends and neighbours.

He has now been handed an eight-month prison term and banned from approaching or contacting his mum and Mr Moreland for the next five years.

Carson was also banned from entering his mum’s street – Mains Drive, in Erskine – and Mr Moreland’s home street – Hillend Drive, in Clarkston – when he appeared in the dock at Paisley Sheriff Court last week.

He admitted sending numerous letters to his mother, who is known as Janet, the police and social work department, claiming he sent them because he was looking out for her.

Carson denied the letters were of a threatening or abusive nature which was likely to cause a reasonable person to suffer fear or alarm and, therefore, illegal.

He sent a host of letters to his mum and Mr Moreland, neighbours of both pensioners and Erskine Parish Church, where his mum went regularly and his father’s ashes are scattered.

In the letters, he branded Mr Moreland “a sleaze”, “a worthless piece of dog poo” and “a vindictive, evil man of malice.”

Giving evidence in his own defence, Carson said he sent them because he was worried for his mum and was looking out for her.

He told the court: “I was trying to put the fear of God into Mr Moreland because of what he’d done to me, my mother and my deceased father.

“I was trying to get rid of Mr Moreland.

“The police wouldn’t do anything - they wouldn’t attend my mother’s house to protect her from Mr Moreland, the social work service also refused to attend my mother’s house.”

Carson added: “I tried everything possible to go down the proper route, to protect my mother, to get rid of him. I wrote the letters to try and protect her.

“At the time, I thought sending the letters out to protect my mother would be within the law. If I’d went up and hit Mr Moreland, that would’ve been outwith the law.

“I wanted to get rid of Ronald Moreland for the immense damage he had caused.

“I’m getting punished because the police and everyone else wouldn’t do their jobs.”

Earlier this year, Carson was found guilty over his poison pen campaign, which he carried out between December 13 and 30, 2014, and sentence was deferred for background reports.

He returned to the dock on Friday to learn his fate.

After hearing that Carson had been assessed by a psychiatrist as having “delusions” and “a fixation” about his mum, Sheriff Seith Ireland jailed him for the offence.

He told Carson: “I am of the view that this is such a serious case that a Community Payback Order is not appropriate. The sentence has to be one of a custodial nature.”