A US father is suing after his son, who has Down's syndrome and autism, was prevented from participating in the Boy Scouts' highest program, wrote BBC.

The local Scout group had previously allowed 15-year-old Logan Blythe to perform modified tasks to gain badges, his father told the Salt Lake Tribune.

But the Boy Scouts of America say that Logan did not fulfill badge requirements and could not progress.

Logan's father, Chad Blythe, is suing the Scouts for a nominal $1.

Logan Blythe had been a Boy Scout for four years and achieved more than 20 badges when his local chapter, the Utah National Parks Council, approved his application to join the Alternative Eagle Scout Program in November 2017.

The program aims to accommodate young people with physical or mental disabilities by allowing them to carry out alternative tasks where they are unable to achieve the standard badge.

But the following day, the family received a text message saying that the national body of the Boys Scouts of America had decided that the allowances previously made for Logan's disabilities meant he did not fulfill the program's criteria.

When the family inquired if there were alternatives to the Eagle program, they were told that participants "must do the requirements as written, including leadership responsibilities", local station KSL-TV reported.

Logan's father, Chad Blythe, has said that the decision effectively voided all of his son's badges.

In a video uploaded to YouTube, Mr Blythe described the case as "the very definition of discrimination".

The Utah National Parks Council said that while they had supported Logan and his family, the decision belonged to the Boys Scouts of America's national body.

Mr Blythe told KSL-TV that he hoped the lawsuit against both the local and national Boy Scouts bodies would bring about change.

"I cannot support an organisation that does not support my son… or support anyone who doesn't support those with mental disabilities, it's wrong," he said.