Dr George Carey said divisions in the Church had reached "crisis" point.
In a farewell address as president of the Anglican Consultative Council, a senior church body, he warned of the danger of breakaway groups emerging.
Dr Carey's speech comes as a number of dioceses in the United States and Canada are planning to bless homosexual "marriages" or unions.
He called on delegates meeting in Hong Kong to urge dioceses to pause before approving such reforms.
It could make life uncomfortable for his successor, Rowan Williams, who is a liberal on homosexuality.
'Erosion'
Dr Carey said: "My concern is that our Communion is being steadily undermined by dioceses and individual bishops taking unilateral action, usually - but not always - in matters to do with sexuality."
He added: "This erosion of communion through the adoption of 'local options' has been going for some 30 years but in my opinion is reaching crisis proportions today."
In his speech, Dr Carey was particularly critical of the Bishop of New Westminster, in Canada, who is reported to have approved a rite for the blessing of same-sex unions, despite the 1998 Lambeth Conference resolutions banning the practice.
He also highlighted the case of a traditional priest deposed by his liberal bishop in the diocese of Pennsylvania.
Dr Carey said this growing chasm between the traditionalists and the liberals in the Anglican faith was his "greatest worry".
In a wide-ranging speech he also addressed the issues of globalisation, the tension between faiths following 11 September and the clash of religions in the world.