Mr Major will pitch his campaign for the final seven days of the election at the heart of Labour's Scottish devolution plans with a speech in Aberdeen warning the Scots that their offer of a Scottish parliament with tax-raising powers would lead to the break up of the UK.
Stepping up the assault on Labour, Mr Major will link the defence of the Union to the Tories' campaign against a federal Europe.
Michael Forsyth, the Scottish Secretary, a key player in the strategy, said: "The big message is that if Labour got into power we might lose our country through the disintegration of the UK and the surrender of power to Brussels in a way that would prove irreversible.
"That is a very important message which is undoubtedly beginning to worry the voters and will determine how many of the doubtfuls which we are still finding will vote."
The Scottish Secretary is spearheading the Tory attack on the so-called Labour "tartan tax" to defend a Stirling seat with a majority of only 703. Mr Major is convinced his campaign will capture the pro-Union votes for the Tories and fulfil a promise to increase the Tory tally of 10 from a total 72 seats in Scotland.
Mr Major will also use the speech to attack Mr Blair's attempts to defuse fears about increased taxes by comparing Labour's proposed Scottish parliament to a parish council. Mr Major yesterday told voters in Perth: "The Scottish Nationalists are honest about it. They are wrong but I respect their honesty. It is more than you can say for the position of the Labour Party whatever that is."
Mr Major ridiculed the apparent U-turns by Mr Blair when he was heckled in the high street in Perth where the Tories lost a by-election to the SNP in 1995 following the death of Sir Nicholas Fairbairn, the former Scottish law officer.
A former Tory councillor, who has joined the SNP, shouted "congratulations on turning the Tory party into an English party". Mr Major retorted the Tories would save the break-up of the UK.
That will be his central message to defend Tory seats against all the odds as he did in 1992. But the Tory strategists also believe Labour's plans are ill-thought out and Mr Blair is highly vulnerable on them.
Mr Major told voters from the platform of his campaign battle bus: "We have to raise this issue. It is an issue that rises above the normal run of politics. It is a battle that many people have not yet seen. It is a battle for the nature of the UK itself."
Mr Forsyth joined the Welsh Secretary, William Hague, in a lions' den for a photo opportunity at Blair Drummond safari park near Stirling, hoping to show their support for the British lion. Instead of cuddly cubs, they were met by fierce animals the size of large dogs with their hackles raised. Mr Major could raise more today by staking his campaign on the Union flag on St George's Day.
If he fails, and the Tories lose the election, Lord Mackay, the Lord Chancellor, became the latest senior Conservative to warn that the Lords may refuse to pass Labour's devolution legislation if Mr Blair fails to allow it to be taken through its committee stage line-by-line on the floor of the Commons.Reuse content