The advice will be part of a wide-ranging review of the adoption laws aimed at persuading social services departments to rely less on dogma and more on common sense.
Health ministers also hope that the review will bring the adoption process into line with other aspects of family law by placing the needs and views of children firmly at the centre of the system.
Older children will be given the opportunity of saying whether they want to be adopted and if they approve of their prospective parents. Natural parents will also be included in discussions about the future of their offspring.
The White Paper will contain recommendations designed to curb what ministers believe to be excessive 'political correctness' in some social services departments.
Social workers will be told that marriage provides the best chance of stability and should be favoured over other forms of relationship. Homosexual and lesbian couples will still be allowed to adopt children, but will be told that married couples should often be given preference.
A Department of Health source said yesterday: 'If, for example, a lesbian couple had special skills in dealing with a particular illness that a child suffered from, it might be appropriate for them to adopt. Nine times out of 10, however, married couples would be more appropriate.'
The equally contentious issue of race will also be addressed by the review. It will say that children should usually be adopted by parents from the same ethnic background, but that hard-and-fast rules are inappropriate.
Sometimes it might be better for black babies to be brought up by white parents, the White Paper will say. It will also tell social workers that they must be more flexible over the age of prospective parents.
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