A 37-year-old man is facing jail after he admitted threatening to kill a Labour MP the day before Jo Cox was murdered.

Geoffrey Farquharson left a message of “venom” on the parliamentary office phone of Ben Bradshaw, the Exeter MP, last month, ending his call with: “I will kill you, you bastard.”

During the two-minute call, Farquharson made comments about Bradshaw’s sexuality and about Muslims.

Farquharson, who admitted sending a communication of an indecent or offensive nature, had introduced himself on the call and given his full address.

Jo Clark, prosecuting, said the case centred on “an abusive and threatening voicemail message” to Bradshaw that was picked up by his Westminster office staff.

District judge Diana Baker described the call as “extremely offensive and very unpleasant”. She said the court should hear it because it was important to get a flavour of what it must have sounded like to the people who picked it up.

Bradshaw said in a victim impact statement to Exeter magistrates court that he had received death threats before and was not unduly concerned.

“I am more worried about my staff in Exeter who have borne the brunt of his behaviour,” he said, adding that the murder of Jo Cox had heightened anxiety over violence towards public servants.

Farquharson, who has a public order conviction from 2005, did not comment in police interviews after his arrest.

His lawyer, Sue Snow, said he sounded “unbalanced and upset” as he made the call.

Baker said Farquharson faced a jail sentence but adjourned for probation and a psychiatric assessment. He was bailed until August for sentencing and warned not to contact Bradshaw or his office, or go to Westminster.

Baker said it was a very unpleasant threat to an MP which contained “venom”.

Farquharson said: “I do apologise for that call.”

Speaking shortly after the call was made, Bradshaw said he, like all his parliamentary colleagues, was stepping up his security. He added: “The security of MPs is constantly reviewed and of course it has as a result of Jo’s murder. We have all been advised to hold appointment-only surgeries – which I think is a sensible caution.

“We have also been advised to let local police know about our movements. But we live in a free democracy and we value and cherish our elected representatives being out and about in public in their constituency.

“I attend hundreds a year that are pre-advertised – none of us want to change that. Politicians driving in armoured convoy and being protected by high walls is not the British way. But it is about getting the balance right and not allowing crimes like this to change our way of life.

“I just feel really numb with grief over what happened to Jo and desperately upset for [her husband] Brendan and her family and loved ones. We all must live with a constant sense of vulnerability.

“I do think we should use this as a moment to reflect as a nation on the political culture we create. And I think politicians and commentators should think more carefully about what they say and do and the influence it has on people and what can open us up to hatred and violence.

“We all must live with a constant sense of vulnerability and this has made us that more acute. I can remember being attacked a couple of times physically during the hunting debate and most of my colleagues have had death threats over the years.”