But, most significantly, Mr Major was also urging the Labour leader to do something the Conservatives have never done themselves; retaining the sovereignty of the Westminster Parliament over European legislation.
Under the treaties of the European Union, European law is mainly initiated by the Brussels machinery, and once it is sanctioned by the Council of Ministers, it becomes supreme law - even to the point of over-riding existing Westminster statute.
The Conservative leader told his daily election press conference yesterday that the danger of the European Social Chapter favoured by Labour was that it would import high European unemployment into Britain, and that once Mr Blair had signed up to it, it would then be locked in for good.
Issuing his challenge to Mr Blair, the Prime Minister then added: "If he thinks it is right to go down the route of the Social Chapter and the Employment Chapter, and all this nonsense he talks about, which will damage our prosperity and our jobs, I make this challenge - Put it through the British Parliament if you are to win the general election.
"The British people can then repeal it, so the British nation can then decide whether it's right, and if it fails the British Parliament can then repeal it.
"Put it through Europe, where it will not have proper debate, where it will have damaging effects on British interests, and it could not be repealed.
"For what credible reason will he not put these vital measures through the British Parliament? If he believes in them, I believe that is what he should do, and I challenge him to say why he will not do it."
Mr Major was asked by The Independent why he had not put European legislation through the British Parliament in the same way, but he did not reply.
In fact, Mr Major's government has even been criticised by the all-party Commons Committee on European Legislation for allowing law to be pushed through the Brussels machine - with the blessing of Mr Major's ministerial colleagues - without MPs being provided with up-to-date drafts in English.
Mr Major said on BBC television Question Time on Thursday night that the Social Chapter "hasn't got much in it at the moment, quite frankly."
But he warned: "It would open up the possibility of all sorts of elements of the European social model being legislated for in Britain by Qualified Majority Vote, but imposed upon British business, adding to their costs and costing us British jobs."
Opening the press conference, Mr Major - for the third day running - put Europe at the top of his agenda, suggesting that the Conservative campaign considers there are net electoral gains to be made from the issue.
In a statement, Mr Major warned that European and British trade unionists were proposing to use European law to give power back to the unions "through Labour's sell-out" to Europe.
"If Labour won, the British government would have to negotiate every new employment law with the European trades unions.
"And British companies - perhaps as small as 50 employees - would have to agree how they ran their business with a union representative on their new works council.
"It might not be beer and sandwiches. More like beer and baguettes. But the danger would be just as great."Reuse content