Atheists could be welcomed into the Scout movement for the first time in 105 years.
The movement, led by TV adventurer Bear Grylls, is launching a consultation to see if members would support an alternative Scout Promise for those who feel unable to pledge a "duty to God".
For more than 40 years, versions of the oath have existed for faith groups including Muslims, Hindus and Buddhists, but this is the first time Scouts have considered an adaptation for atheists.
The proposed changes are designed to increase diversity in the movement and enable more young people and adults to join.
Leaders insist the existing Scout Promise - which also contains a vow of allegiance to the Queen - would continue to be used alongside alternative versions.
Wayne Bulpitt, the association's chief commissioner in the UK, said: "We are a values-based movement and exploring faith and religion will remain a key element of the Scouting programme. That will not change.
"However, throughout our 105-year history, we have continued to evolve so that we remain relevant to communities across the UK."
Membership of the Scouts has risen during the past seven years from 444,936 in 2005 to 525,364 this year, figures released by the association show.
Since 2002, the number of girls taking part has increased by 69% while more than 50 scout groups catering for young people drawn mainly from Muslim, Hindu and Sikh communities have opened in the last 10 years.
The Scout Promise reads: "On my honour, I promise that I will do my best to do my duty to God and to the Queen, to help other people and to keep the Scout Law."
Alternative versions allow Hindus and Buddhists to use the word "my Dharma" while Muslims can use the word "Allah".
Non UK citizens are permitted to replace the phrase "duty to the Queen" with "duty to the country in which I am now living".
Terry Sanderson, president of the National Secular Society, said: "If the Scouts decide to change the promise, it would relieve many young people of having to lie about what they believe in order to be part of this great organisation."