The leader of the English Defence League, Tommy Robinson, has announced he is leaving the organisation, saying it has become too extreme and its street protests are no longer effective.

Robinson, who led anti-Islam demonstrations that often turned violent and were marked by racist chanting, said he had not changed his views but realised Islamist ideology should be challenged "not with violence but with better, democratic ideas".

Robinson, who set up the EDL in 2009 ostensibly to combat extreme Islamism in the UK, is facing criminal charges in relation to his activities with the group. The 30-year-old from Luton, whose real name is Stephen Yaxley-Lennon, said: "I have been considering this move for a long time because I recognise that, though street demonstrations have brought us to this point, they are no longer productive. I acknowledge the dangers of far-right extremism and the ongoing need to counter Islamist ideology not with violence but with better, democratic ideas."

His decision was announced in a press release from counter-extremism thinktank the Quilliam Foundation, which said it had "facilitated" Robinson's departure and that of the EDL co-founder, Kevin Carroll, also from Luton. Quilliam said it would provide them with lessons about Islam and training in lobbying institutions.

The intentions of the pair, who are expected to set up a new political movement, are likely to come under intense scrutiny given their past activities.

Some Muslim and anti-facist groups gave a cautious welcome to the news but there was a sense that Robinson would have to go further to make up for the harm they said he had inflicted on community relations over recent years.

Robinson and Carroll are due to stand trial on 16 October for allegedly attempting to defy a ban on marching to the scene of soldier Lee Rigby's killing in June.

During interviews and at a press conference in London alongside Maajid Nawaz, co-founder and chairman of the Quilliam Foundation, Robinson said he had realised the EDL had become "part of the problem" in his quest against Islamic extremism, rather than a solution.

"I apologise if what I have said and represented has not resonated individually with Muslims," he said, when asked if he had any regrets.

He made a decision to leave the EDL after getting out of prison and finding that "fringe elements" such as neo-Nazis had been invited back into the EDL's ranks.

However, Robinson consistently refused to renounce past statements such as his declaration of opposition to the building of all mosques "because they preach homophobia and antisemitism".

Carroll insisted that he and Robinson were "still singing the same song" and warned Britain faced the prospect of "sectarian conflict" in five to 10 years.

There was a mixed reaction to Robinson's announcement from EDL supporters. Some accused him of selling out but others praised him. Robinson tweeted : "The most difficult day of my life! I thank Edl supporters for their messages of support. For me this is a step forwards not backwards."

Robinson's personal assistant, Helen Gower, told IBTimes UK that Robinson and Carroll would be forming a new group that was not street-based.

Mohammed Shafiq, chief executive of the Ramadhan Foundation, said he had met Robinson last week. "During that meeting he indicated that he was leaving the EDL because he couldn't control the extremist group," Shafiq said.

"At no stage did he reject his previous disgusting attacks on Islam and Muslims or apologise to the British people for the millions wasted policing their protests."

Nick Lowles, director of Hope Not Hate, which campaigns against extremism, said: "We celebrate Quilliam's efforts here but only a complete renunciation of the violence and hatred the EDL leaders have promoted, and a turning away from the anti-Muslim rhetoric they have championed, will be enough for the many thousands who have suffered from the EDL's ugly actions over the past three years."

Quilliam, which has received government funding, is better known for its work combating Islamic extremism but it has faced criticism in the past for accusing peaceful Muslim groups of sharing the ideology of terrorists.

It described the move by Robinson and Carroll as "a huge success for community relations in the United Kingdom" and urged others, both in the EDL and Islamist groups, to follow in the pair's footsteps and abandon extremist ideologies.

Nawaz said: "As well as being a very positive change for the United Kingdom, this is a very proud moment for Quilliam.

"This represents not a change but a continuation for us, as challenging extremism of all kinds forms the basis of our work.

"We have been able to show that Britain stands together against extremism regardless of political views and hope to continue supporting Tommy and Kevin in their journey to counter Islamism and neo-Nazi extremism."