The government yesterday delayed a decision on whether to end anonymity for future sperm and egg donors at fertility clinics although some people born as a result of early assisted reproduction procedures will have the chance to identify their biological parents.

Ministers want clinics or charities to run a voluntary register through which children conceived before regulation of the fertility industry began in 1990 could make contact with donors or half-brothers and sisters.

Public health minister Hazel Blears suggested a pilot scheme at a conference of fertility experts but failed to mollify many frustrated at the delay on the wider issues. She confirmed, however, that children born from donations after 1990 will have the right to non-identifying pen-portraits of their genetic parents when they turn 18.

There have been rows over continuing anonymity, with its own regulators in the human fertilisation and embryology authority trying to bring change. But only 18 of 114 fertility clinics gave any view on the issue during a consultation.

Of about 9,000 assisted conceptions in Britain last year, 1,300 were the result of donation, mostly of sperm.

Marilyn Crawshaw, of Progar, an umbrella group pressing for change, said: "We think it is indefensible there can be a state-sanctioned secret."