The Girl Guides are considering whether to remove any mention of God or the Queen from their oath.
The voluntary organisation, which boasts more than half a million members, has launched an online consultation into changes to the pledge that Guides take when they join, known as the Promise.
Girlguiding UK said the move was necessary because an increasing number of girls and volunteers do not identify with the current oath.
In a statement the organisation said: "The Promise is guiding's beating heart - it is the core expression of values and the common standard that brings everyone in guiding together.
"Over the past few years we have heard from more and more girls and leaders who struggle with the wording, particularly in interpreting what it really means to girls today.
"Girlguiding UK is committed to retaining a Promise that is in line with its original principles, but we know it is crucial that girls and young women understand and believe in the words they say."
Guides currently promise to "love my God" and "serve the Queen and country", as well as do their best, help other people and keep the Guide law.
Respondents to the consultation are asked to express their preferences for alternatives such as "do my duty to God", "be true to a higher ideal" and "serve the highest truth and love faithfully at all times".
Options mooted to replace the current mention of the Queen include "serve the Queen and my country", "engage myself with responsibility in the community I live in" and "be true to my country".
The move towards a new oath has been seen as an attempt to attract a new breed of volunteers to lead the Guides.
Last year 50,000 girls were on waiting lists to join the 102-year-old organisation because of a lack of trained leaders, according to reports.
But it also reflects a modernising leadership, with new Girlguiding UK chief executive Julie Bentley telling The Times in November that the Guides are the "ultimate feminist organisation".
Last month, the Scout Association also announced it had launched a consultation to see if members would support an alternative Scout Promise for those who feel unable to pledge a "duty to God".
The Guides' consultation, which is open to members and non-members, will close on March 3.