Dr John Marks, a member of the School Curriculum and Assessment Authority and a campaigner for more selection, said non-selective schools doing well would be bound to survive.
Labour dismissed John Major's grammar schools expansion, saying it would cost pounds 2bn, and highlighted a Cabinet split on the issue.
Dr Marks said the change would be a gradual one. "There may well be a return to more grammar schools, but it won't mean the end of comprehensives. There are many good comprehensive schools. I don't see why they should not remain where they are doing a satisfactory job," he said.
However, he argued that the new policy would raise standards. Even the average secondary modern school had exam results better than the worst quarter of comprehensives, he said. There should be more technical schools as well.
Others believe the policy will have little effect. Only a handful of the existing 1,000 opted-out schools have applied to select pupils by academic ability, and most head teachers say they are happy with the current system. In Solihull and Lincoln, plans to bring back selection have foundered because of parental opposition.
As new details emerged of the proposals, Labour claimed Gillian Shephard, the Secretary of State for Education and Employment, had been forced into "an extraordinary U-turn" by Downing Street. For years she had supported non-selective schools, said Labour's education spokesman, David Blunkett. The reform, first announced by Mr Major last September, will give the funding agency for grant maintained schools the power to build new grammar schools from scratch.
Mrs Shephard is believed to have supported the abolition of grammar schools in Norfolk after she became a Conservative councillor there in 1977. More recently she has expressed reluctance to return to a selective system. Just after her appointment she told the Independent: "I am much more interested in specialist schools than in selective schools."
Yesterday Mr Blunkett said Mrs Shephard had been an enthusiastic opponent of selection. "Now she seems ready to embrace a philosophy which will appease the Downing Street policy unit. She will have very little credibility indeed when she puts forward her proposals in the Commons (tomorrow)."
An analysis carried out for Mr Blunkett shows that it would cost pounds 2bn to build 200 new grammar schools to educate 60,000 pupils - less than 2 per cent of the secondary school population. The money would be enough to pay for full-time nursery education for all three and four year-olds.
Yesterday Labour party officials said the plans could create surplus places in other schools and upset existing, non-selective schools which had suffered cuts in funding for building work. Neither the Department for Education and Employment nor Conservative Central Office had any comment to make yesterday.Reuse content