The advert claims adoption is a quick process, saying there is "no cost", "no waiting time" and "no hoops to jump through". It was placed in three local newspapers in Cambridgeshire, but the children are not local and their names have been changed in a bid to protect their identity.
Adoptionplus was commissioned by a local authority, which cannot be named for child protection reasons, to find the boys a home.
Joanne Alper, a service director at Adoptionplus, defended the adverts, saying the company needed to find an imaginative way to encourage adoption, as the number of children looking for a home had grown.
"Basically the situation is there are 4000 children in the UK who need a family and a lot of authorities are struggling to find them.
"There is a lot of pressure on them to try and be a bit more creative. This advert is a new thing. It is us trying something different and it is unusual. ... We want to do everything we can."
MP John Hemmings said it sent out the wrong message and would not serve the purpose of finding a safe home for vulnerable children.
The Liberal Democrat said: "If parents with children did something like that they would go to jail ... They seem to be unconcerned about the household that children end up in. It is about box-ticking rather than finding them a good home."
Adoptionplus is monitored by watchdog Ofsted and was rated as "outstanding" in February.
The British Association of Adoption and Fostering said they welcome new ways of encouraging prospective parents. A spokesperson for the charity said: "It's not something new to us as we are always trying to find ways of rehoming children. We are very careful about where we feature children. We normally change their names or don't talk about location."