The Bill, which was published on Monday, will make it illegal to treat anyone over 18 unfairly in the 'provision of goods, facilities and services' on the basis of their age.
Harriet Harman, Leader of the House of Commons, decided that children and young people will be excluded from the protection.
She told MPs, 'The provisions will not cover people under 18. It is right to treat children and young people differently.'
She added, 'There is little evidence of harmful age discrimination against young people.'
But the Young Equals coalition, a group of children's charities that includes the Children's Rights Alliance for England, the Children's Society and Save The Children, says that age discrimination is the most common form of unfair treatment experienced by children.
It cites examples of discrimination such as babies being refused entry to buses, and the high-frequency 'mosquito' devices used to deter teenagers from certain areas, which can cause babies and young children distress they may be unable to articulate.
Bob Reitemeier, chief executive of the Children's Society, said that ministers are 'making a huge mistake by exempting under-18s from the Equality Bill, and are sending out a stark message to children that the Government does not think they should be given the same rights and respect as adults'.
The Bill, which is due to become law within a year, will require all public bodies to show evidence of how they are offering equal opportunities covering gender, age, race, religion and sexual orientation. In a move to close the pay gap between men and women, the Bill will require companies to publish what pay their staff receive in a 'gender pay audit'.
