The Federation of Zionist Youth is being threatened with legal action after telling a 16-year-old boy that he could not attend its summer Israel tour.

Ryan Lipman, who suffers from obsessive-compulsive disorder (OCD), was told less than two weeks before the trip that he would not be able to attend because of his medical condition.

He had already taken part in the orientation activities, and was due to leave this week.

Now his parents, Errol and Lisa Lipman, from Hampstead Garden Suburb in North-West London, have threatened to sue the movement on grounds of discrimination.

Mr Lipman, a property-company director, claimed that FZY was discriminating against Ryan. He said that the disorder affects his son’s eating, and led to his being severely underweight earlier this year.

“We told him that unless he put on a pound every week, then he could not go on Israel tour,” Mr Lipman said. “He worked so hard and managed to achieve that. It was an extraordinary feat, but now he has been told he cannot go.”

His mother said that both she and her husband were confident that Ryan’s OCD would not be a problem if  he were to attend the tour.

“Ryan is very well-versed with his condition. Three months ago we would not have sent him on tour, because he was not well, but now he is out of the danger zone in terms of his weight,” she said.

Mrs Lipman said that she had told FZY that should her son, who attends London’s Immanuel College, be unwell, she had family friends in Israel who could pick him up within half an hour.

“I could also be there in half a day,” she said. “He is so upset by this. They all look forward to Israel tour for such a long time and all his friends will be going. FZY is stigmatising him.”

Ryan said: “My OCD does not feature when I’m around my friends and I have been on previous FZY summer camps.

“I was shocked when I heard I couldn’t go. I was in tears that evening because I had been so looking forward to it.

“All my friends are going and I just want to spend the summer with them. I would do anything to go.”

He added that not going on the trip would be like “not being able to go on the best ‘end of GCSEs’ party”.

FZY insisted it could not comment on any individual medical cases. Its national director Jonny Bunt said: “Medical information is given in the strictest confidence and we hold it as such. We consult medical professionals in all questionable medical cases.”

Ryan’s friends have been so shocked by the movement’s decision that four of them set up a Facebook group in his support. At the time of going to press, 235 people had joined Ryan Lipman Should Be Allowed To Go On Tour.

Oliver Craig, one of those who set up the group, was due to be in the same tour group as Ryan.

He said. “I’m so annoyed and upset for him that he’s not allowed to have the same opportunity to go to Israel. He tried his best and did everything he could to get on tour, and that’s what really annoys me.”

FZY’s popular month-long Israel tour, aimed at teens who have completed their GCSE exams, is designed as an in-depth introduction to the country, and includes hiking and a variety of  other activities. It attracts hundreds of youngsters every year.