A racist internet troll has been found guilty of harassing a Labour MP with a series of anti-Jewish rants sent after the jailing of a fellow far-right extremist.

Joshua Bonehill-Paine, who turned 24 on Wednesday, wrote five hate-filled blogs about Luciana Berger, the MP for Liverpool Wavertree, after Garron Helm was sent to prison for four weeks in October 2014.

The jury at the Old Bailey deliberated for just over one hour and 15 minutes before finding Bonehill-Paine guilty of racially aggravated harassment.

Garron, then 21 and from Merseyside, had admitted tweeting a picture depicting Berger, 35, with a Star of David on her forehead with the hashtag “Hitler was right”.

Luciana Berger arrives at the Old Bailey on Wednesday. Photograph: Dominic Lipinski/PA

Over the next four months, Bonehill-Paine posted articles calling her a “dominatrix” and “an evil money-grabber” with a “deep-rooted hatred of men”. In one, he claimed the number of Jewish Labour MPs was a “problem”.

He illustrated his posts with offensive pictures, including a rat with Berger’s face superimposed on it.

Bonehill-Paine hailed the “Filthy Jew Bitch Campaign” led by US white supremacist site Daily Stormer as “fantastically successful” after the MP was sent 2,500 tweets.

Throughout, Bonehill-Paine, of Yeovil, Somerset, was on bail awaiting sentence for making claims on Twitter that several people were paedophiles.

Giving evidence, Berger said the posts had made her feel sick and “under attack”. She told jurors she feared for her safety because “what happens online does not always stay online”.

The MP said: “It’s fair to say I was the most concerned I have ever been about my personal safety since I was elected … In the midst of this ‘Filthy Jewish Bitch’ campaign the police were in constant contact with me. They were in my office and home and assisted my personal safety.”

James Palfrey, for Bonehill-Paine, described the posts as “satire” and “pathetic puerile rubbish” and argued that they fell within the right to freedom of speech.

But Philip Stott, for the prosecution, said the defendant had refused to face questions in the witness box because he had no “sensible” answer to the charge.

The jury was not told that the defendant, a former hospice worker, is already serving a jail sentence for posting antisemitic material. He was found guilty of inciting racial hatred in December last year for producing a flyer advertising a neo-Nazi rally in Golders Green – an area of north London with a large Jewish population – that featured a picture of the Auschwitz concentration camp and promised the event would be “a gas”.

Bonehill-Paine, who smirked in the dock as he was sent down, faces up to two years in jail when he is sentenced on Thursday. His conviction comes days after neo-Nazi Thomas Mair, 53, was handed a whole life term at the same court for murdering the Labour MP Jo Cox.

Earlier this year, another internet troll, John Nimmo, 28, from South Shields, was convicted of making a death threat against Berger by saying she would “get it like Jo Cox”.

In his first email of 6 July, he told Berger: “Justice for Joshua Bonehill-Paine will be sweet, he has friends everywhere. Watch your back Jewish scum, regards your friend the Nazi.”

He then followed it up two days later with “You will get it like Jo Cox did, you better watch your back Jewish scum” just as Berger was leaving her office in the early evening.

Nimmo was previously jailed in 2014 for eight weeks for tweeting abusive messages to the feminist campaigner Caroline Criado-Perez and the Labour MP for Walthamstow, Stella Creasy.