The UK government is planning to speed up the the process which agencies say is due to legal problems and a shortage of suitable adoptive parents.

But they add that cases have become a lot more complex in recent years.

This is because of a shift in social attitudes towards adoption.

In 1975, 22,000 children were adopted in the UK.

Just over 20 years later, that number has fallen to about 6,000 a year and half of these are step-family adoptions.

This is when a step-parent seeks to be considered the legal guardian of a child to help them feel more at home in their new family.

In the 1950s and 1960s, the stigma attached to being a single parent meant many unmarried women who became pregnant felt obliged to put their babies up for adoption.

Nowadays, being a single parent or living with a partner is more accepted.

Talk Adoption, which runs a national helpline for young people, says the pendulum against adoption has swung so far that it is receiving calls for pregnant teenagers who complain that they are not given any support when they say they want their child to be adopted.

Social workers say this is because many change their minds after the birth of the child, but Talk Adoption manager Sarah Forster says this is "irrelevant".

"Young people need support about their decisions at the point when they take them. We all change our minds sometimes," she said.

Complex problems

Because of the reduced social stigma about single parents, children put up for adoption also tend to be older, to have a history of abuse or neglect and to have been in several foster or care home placements.

However, adoptive parents still tend to prefer younger children, particularly babies.

Adoption agencies say there is a national shortage of suitable parents coming forward and many do not want older children with more complex problems.

For this reason, they have set up National Adoption Week, which this week celebrates its third anniversary.

The aim is to get more parents to come forward.

Another factor which has delayed the adoption process is a legal conflict between adoption legislation and the Children Act 1989.

The latter emphasises the interests of the child, but adoption legislation does not have this at its heart.

The British Agencies for Adoption and Fostering (BAAF) says this can lead to lengthy challenges from birth parents.

"The law needs to be updated so that the paramountcy of the child's interests is at the centre," said a spokeswoman.

"This might mean a judge would decide that the best thing for the child is a quick decision which gives them stability."

Adoption process

Before an adoption takes place, a prospective parent has to be assessed by social services.

Each local authority may have different criteria on who they consider a suitable parent.

Some children face long delays in the adoption process

There has been much media coverage of a handful of cases where parents have been turned down for being overweight or smoking.

The assessment procedure usually takes between six and nine months.

If there are no problems, the parents then have to wait to be matched with a suitable child.

The BAAF says this can take three months or longer.

The government has issued guidance to local authorities urging them to speed up the whole adoption procedure.

It is worried that delays mean children face considerable disruption to their lives and are often moved from placement to placement while they wait for a decision.

This can have a damaging effect on their emotional and educational development.

Talk Adoption says some cases can take six years to process.

It says that, in the past, social workers have resorted more to temporary placements because they believe it is better for the child to keep contact with their birth parents, if at all possible.

Adoption has been seen as too much of a break.

Contact

But nowadays there is much more emphasis on keeping contact with the child's natural family after adoption.

"Many teenagers who ring our helpline say they want very basic information, such as what their birth parents look like and what their health record is," said Sarah Forster.

"They want to establish their own identity and that is a very important part of growing up."

She added that there was still some stigma attached to adoption and this made it difficult for children to talk about it.

Many felt isolated because they could not talk to their adoptive parents for fear of upsetting them and their friends did not understand, she said.

She hoped that raising awareness about adoption would make it easier for people to discuss their feelings.