Margaret Thatcher began plotting to defeat the coal miners from the day she took office, according to her official biography published today.

The new Prime Minister put her deputy, Willie Whitelaw, in charge of the preparations for a showdown with the National Union of Mineworkers (NUM).

However she was forced to postpone the confrontation until her second term of office after warnings that she was not in a strong enough position to win.

The details are disclosed in Margaret Thatcher, The Authorised Biography – Volume One: Not For Turning, by former Daily Telegraph editor, Charles Moore.

Mr Moore was given full access to all her personal and government papers as well as interviewing her, her family and those who worked most closely with her.

According to the book, when she entered office in May 1979, she was determined to avenge the defeat of Edward Heath’s Conservative government, which was brought down by the NUM five years earlier.

“She summoned Willie Whitelaw and Sir Robert Wade-Gery, the Deputy Secretary to the Cabinet and announced: ‘The last Conservative government was destroyed by the miners’ strike, and we’ll win. And you, Willie, will do it’,” Mr Moore wrote.

As chairman of the of the Civil Contingencies Unit, Mr Whitelaw tried to draw up “strategic principles and practical measures”. However he was hampered by the Treasury which wanted to run down coal production rather than build up stocks for a strike.

In Whitehall, there was little enthusiasm for a confrontation. Sir Robert recalled people were saying “The woman’s mad. You can’t win miners’ strikes. All you can do is buy them off”.

In September 1980, Energy Secretary David Howell presented his plans within government for closing down uneconomic, high-cost pits.

Mrs Thatcher was unimpressed, writing on her copy of the document “Thin”.

Nevertheless by February 1981 it was clear that they could be sufficient to provoke a new miners’ strike – backed by their allies, the steelworkers and the railwaymen.

At this point, Mrs Thatcher’s trusted press secretary, Bernard Ingham, stepped in to warn her that they were trying to do “too much, too quickly”.

At meetings on February 16 and 18, it became clear that the government was just not ready for a strike and the coal stocks could not withstand one.

“As Howell remembered the first meeting, Mrs Thatcher held up a copy of the Evening Standard which Mr Ingham brought in with the words, ‘That’s that, then, isn’t it?’ The headline proclaimed, ‘Government dithers’,” the book states.

“Mrs Thatcher said, ‘Bring it to an end, David. Make the necessary concessions’. Without Cabinet discussion, she decided to give in.”

Mr Howell said that while he resented her anger towards him for his handling of the matter, he believed she was right to “cut and run” as “we just weren’t ready”.

It was, however, a confrontation postponed. The showdown with the NUM had to await her second term following her 1983 general election victory.

Owen Smith, Shadow Welsh Secretary, said: “This merely confirms what we’ve known all along: that Mrs Thatcher coldly and calculatedly set out to provoke a conflict with the miners in order to break the union and close the pits that provided employment for so many in our communities.

“Vengeance for the miners’ strikes of the early 1970s and their impact on the Tory Government was clearly her primary motive, rather than any high-minded attempt to reform the British economy or industrial relations, and many in Wales will never be able to forgive her for the manner in which the miners were treated or for the compassionless and precipitate way in which the pits were subsequently shut down.”