A PRE-OP transgender killer is to have a £20,000 sex change - and the British tax payer will be picking up the bill.

Paris Green, 23, who was born Peter Laing but identifies as a woman, has been on a waiting list for an operation on the NHS.

Prison authorities allowed her to live in the women’s wing of HMP Edinburgh while she waited for her gender reassignment surgery.

But the sick killer – who helped torture somebody to death after a row over a bag of chips – was found to be having sex with female lags.

Now, according to Mail, she is to receive full ‘gender reassignment’ surgery paid for by the taxpayer.

Her victim's sister, Pauline Bell, 46, told the paper: "She should not be getting the operation on the NHS. It’s not lifesaving treatment. She took somebody’s life away and destroyed a family.

"I’ve got absolute sympathy for transgender people. Let them have the operation. But not her."

Writing from jail, Green confirmed to the paper: "I am having the op, and pretty soon. The letter has went out [sic] to the surgeon asking him to take on my case."

In January last year, screws were forced to send her back to the men’s wing when she ignored them and kept hooking up with her fellow prisoners.

Shockingly, this is not the first time Green has had to be moved after taking advantage of the system to enjoy care-free sex with other convicts.

In 2013 she was moved from Corton Vale women’s prison, near Stirling, after reports of “inappropriate behaviour” with women at the jail.

She was jailed for a minimum of 18 years in 2013 for her part in the brutal murder of Robert Shankland, 46, in Glenrothes, Fife.

Green and two pals lured their victim back to a flat before tying him up and battering him to death after sexually assaulting him with a rolling pin.