POLICE are investigating a poison pen letter claiming that terrorists plan to behead Tasmanian Senator Jacquie Lambie unless she helps introduce sharia law in Australia.

The letter warns that “you are the enemy of Islamic State, therefore, I will take the honour in beheading you”.

It includes graphic images of a man having his head sliced off by a knife.

Her office conceded the letter could be a fake threat, linked to opponents of a new mosque in Adelaide, but said that they were taking the threat seriously and had referred the matter to the Australian Federal Police.

It claims to have been prepared by the “Adelaide Islamic State Mujahideen” and makes references to plans to build a mosque in Adelaide, suggesting that the development would represent a celebration of Lindt gunman Haron Monis’s efforts to expand the Islamic State’s philosophy.

The outspoken senator, who recently called for the introduction of the death penalty for terrorists, has confirmed her staff received a letter this week.

“Do not involve the police or media, shut you f---en mouth and do as I say or else the bloodshed will worsen,” the letter says.

“I swear upon Allah’s will that death will be approaching to you.”

Describing the contents as “disgusting” Senator Lambie said she had no plans to abandon her pursuit of tougher laws against terrorists.

“If you don’t like our Australian law or you don’t want to abide by our Australian constitution then pack your bags and do what I have already asked leave,” she said. Here is a reality check for Islamic terrorists living in Australia, we will never bow down to sharia law.”

Opponents of the proposed mosque at Greenfields yesterday distanced themselves from the letter. John Bolton, who made a deputation against the mosque being built at a Salisbury Council meeting last week, said the letter was shocking.

“My belief is there are very good arguments to why the mosque should not be built there (but) I would not be involved with, nor am I aware of, anyone who would make such statements,” he said.

A member of the Patriots Defence League of Adelaide, who did not want to be named, said he did not know of anyone who would go to such extremes and would not endorse such a horrific letter. He said he would be sceptical of the letter being created by anyone in the League but said he could not speak for everyone.

Ahmed Ahmedy of the Hazara Foundation of SA, who have proposed the mosque., said he was shocked anyone would try and link the mosque with the crimes of Monis.

“I don’t know what the beliefs of the people who did write the letter are but it is not an Australian belief,” he said.

“Australians are broad minded and multicultural.”

SA Police Assistant Commissioner Bryan Fahy said SA Police were aware of the threat and working with Australian Federal Police.