Leaders of the 750,000-strong movement reaffirmed their belief that young women worked best in all female organisations.
Jane Garside, the association's Chief Commissioner, said that the Guides' emphasis on exclusively female packs had once been unfashionable. Now everyone from educationalists to feminists was coming round to the Guides' way of thinking.
'Research figures prove that young women do produce better results when they are without the competition of young men,' she said. 'We feel that girls develop better and achieve their full potential with their own sex.'
In a 'vision statement' for the 1990s, the Guides said that they wanted their members to mature into 'confident, capable and caring women', who would realise their potential in their career, home, personal life and as citizens. The Guides believed that they could 'best develop these qualities in a mutually-supportive female structure, within an environment of fun, friendship and adventure, underpinned by spiritual and moral values'.
The single-sex line was a response to the announcement 18 months ago that the Scouts wanted to recruit girls.
The Scout movement was unable to say yesterday how many girls had been signed up since. But senior Guides said that the Scouts' initiative had been a disaster and hardly any girl members had gone over to the boys. The failure of the Scouts to recruit had been exposed by a 22,364 rise in Guides' membership last year.
The change in the movement's name from the Girl Guides to the Guides Association reflected the organisation's emphasis on recruiting women aged 18 to 25.
Mrs Garside explained the new direction by pointing out that more than 75,000 women aged 18 or over are in the Guides. 'Many are married. Why should they be members of an association whose title implies that they are girls?'
The new image will not be accompanied by a change in policy. Leaders of the movement said its members were already told about sex education, Aids, drug abuse, homelessness, the poll tax, gambling, drinking and breast cancer.
The name decision caused ripples of dismay at Westminster. Elizabeth Peacock, president of Batley Scout Council, and Conservative MP for Batley and Spen, said: 'It's a shame. I know they are trying to move into modern times, but the Girl Guides has long been an association that is recognised and everybody knows what you are talking about.'
Ann Winterton, Tory MP for Congleton, said: 'It's a bit silly. They are going to remain, quite rightly, a single-sex organisation. If that is the case, why should there be a change of name?'
But a Labour newcomer, Bridget Prentice, MP for Lewisham East, said: 'I think it is a progressive move and long overdue.'