Former Ukip leader Nigel Farage has called for current leader Gerard Batten to be ousted from the party over the decision and said that involving Robinson in the party will drag Ukip in a “shameful” direction.
Robinson - real name Stephen Yaxley-Lennon has been appointed as an adviser on rape gangs and prison reform to Ukip leader Gerard Batten.
Mr Batten said the English Defence League founder had "great knowledge" about the subjects.
Robinson was jailed for 13 months for contempt of court in relation to his activities filming people involved in a grooming case.
The sentence was later quashed and the case has been referred to the Attorney General.
Mr Batten said: "I have appointed Tommy Robinson to be a personal special adviser on two subjects which he has great knowledge.
"It is not necessary for him to be a party member in order to assist me in this role.
"I am looking forward to working with him."
Robinson has had a series of run-ins with the law.
Robinson was also imprisoned in 2013 for using someone else's passport to travel to the US.
Other convictions include drugs and public order offences and he was jailed in 2014 for 18 months for mortgage fraud.
He said that "going to prison was the best thing that ever happened to me" after the passport conviction.
Former Ukip leader Nigel Farage has said he is "appalled" that Tommy Robinson has been appointed an adviser to the current party head Gerard Batten.
"But Gerard Batten has got this, sort of, fixation with Tommy Robinson and discussing Islam, and dragging Ukip into a direction of effectively being a, sort of, street activist party."
Mr Farage added: "It goes against all the things I did as leader to say we will talk about immigration, we will talk about the extreme forms of Islam. But, we will do it as a non-racist, non-sectarian party.
"This blows a hole in all of that."
Asked if the appointment was the end of Ukip, Mr Farage said: "Well, I haven't given up yet.
"I will be writing to the National Executive Committee of the party today and urging that we have a vote of no confidence in Gerard Batten as leader. That we get rid of him.
"We can have one last go at getting rid of somebody who as leader is dragging us in a shameful direction."