A significant number of children in care are losing out because of long systematic delays in approving adoptive parents, according to an Adoption UK survey.
The survey of the charity's membership and website users, found that while many of those interested in adopting receive a good or reasonable response from adoption agencies, over a quarter were turned away.
Of the survey's 172 respondents, 27 percent were turned away. Sixteen percent of those who gave a reason for the rejection claimed the agency was not recruiting adopters. The figures come at a time when there are approximately 4,000 children in the UK care system waiting to be adopted.
Adoption UK Chief Executive, Jonathan Pearce, said: "While the majority of adopters going through the process to become adoptive parents are experiencing good practice, too many are subjected to long wait times and bad practice - if they get through the front doors of the adoption agency at all.
"While some applicants will not be suitable to adopt, far too many people are not being given due consideration, and the delays that many experience are simply not good enough when we have thousands of children waiting to be adopted into homes where they can be helped to reach their full potential", he added.
The survey also revealed that 13 percent of respondents were turned away on the grounds that their ethnicity did not match the ethnicity of the children in the agency's care.
The former chief executive of Barnardo's, Martin Narey, has warned that local authorities' "prejudice" against arranging mixed ethnicity adoptions was leading to a collapse in adoption rates.
Speaking to the Guardian Mr Narey said: "The law is very clear. A child should not stay in care for an undue length of time while waiting for adoptive parents of the same ethnicity.
"But the reality is that black, Asian and mixed race children wait three times longer than white children."
The Adoption and Children Act 2002, which came into force at the very end of 2005, sets out timescales to which agencies should adhere during the preparation, assessment and approval of adoptive parents.
The Act states that prospective adopters should be invited to an adoption information evening within two months of their initial inquiry. Of the survey's respondents, 69 percent were invited within three months of their inquiry but 31 percent waited three months or longer and 10 percent did not receive an invitation for longer than six months.
Mr Pearce said: "This research shows that those people coming forward to adopt are often met with poor and inconsistent service - an approach that will deter many prospective parents altogether.
"Furthermore, for two-thirds of our respondents it took less than one year for a child or sibling group to be placed but for one-third it took longer than one year. For 6 percent, it took longer than two years. This is far too long and means that there are children experiencing further trauma from staying in care too long or from moving between multiple foster placements," he added.