LONDON — MARGARET THATCHER'S advisers hope her new focus on the condition of the family will be the key to continuing the rule of her Conservative Party well into the 1990s. In the past decade, the British prime minister has hurled back the Argentine invader from the Falkland Islands, curbed the overweening power of trade unions, and offered British people a chance to harness market forces to personal profit. All this had powerful voter appeal.
This time she has decided to focus on a central social issue: the plight of the family in modern society and the penalty individuals have to pay because of the buffeting family life has undergone.
In a speech last month intended to be the keynote of a sustained political initiative, Thatcher warned that hundreds of thousands of children were in danger, because of a progressive weakening of the family. It was, she said, a greater challenge to Britain than the deterioration of the physical environment.
The prime minister's address, in which she noted that Britain had the highest divorce rate in Europe, was soon followed by a speech by Kenneth Baker, the Conservative Party chairman. Mr. Baker said the family was going to be a ``key issue'' on the British political agenda for the 1990s. The number of single-parent families, he said, had doubled to more than 1 million in the last 20 years - 1 family in 7 in Britain.
The party chairman's comments are being sent to all prospective Conservative parliamentary candidates, who are urged to incorporate them in future speeches of their own. This means that family questions will become the subject of political debate in every city, town, and county in Britain in coming months.
The decision to make the condition of the family a cardinal issue in British politics follows research carried out by the Centre for Policy Studies, a Conservative Party think tank that has provided the philosophical underpinning for many of Thatcher's most popular policies.
Thatcher in her keynote speech cited the fact that four out of five solo mothers claiming income support from the government received no maintenance from the fathers. ``No father should be able to escape from his responsibility,'' she said. On the same day she ordered the secretary of state for social services, Tony Newton, to begin a blitz on defaulting fathers - a policy already followed in the United States, and in Australia where the proportion of fathers paying maintenance was raised from 30 percent to 70 percent in the late 1980s.
In Britain, the cost of state maintenance for one-parent fathers now runs at 1.85 billion pounds ($3.2 billion) annually. Reacting to Thatcher's remarks, Michael Meacher, the Labour Party opposition social services spokesman, accused her of using concern for the family as a cloak for wanting to save money.
``She is not concerned with the welfare of single-parent families, but only with reducing the government's expenditure on income support,'' he said.
Independent research suggests that in the family Thatcher may have hit upon a potent theme for the future.
A report by the National Family Trust, a nonsectarian Christian organization, says that members of more than 9 out of 10 families lead separate lives under the