The proposals, some of the toughest employment legislation since the Second World War, provoked outrage among trades unions and raised doubts among some Tory supporters.
Senior Tory sources said the Government had decided to press ahead with the plans, outlined in a Green Paper last year, which proposed that unions could be stripped of immunity from legal action if a court decided the effects of the strike were "disproportionate or excessive'.
The notice period for strikes could be doubled to 14 days after ballots where a majority of those entitled to vote would be needed to make the strike legal.
The TUC attacked the proposals as "vindictive and small-minded". It could leave unions open to injunctions and fines for contempt of court with sequestration of assets.
The Green Paper made it clear that strikes last year affecting the fire service, London Underground and the Royal Mail would have come within the scope of the new measures.
Tony Blair this week told the unions that "the basic trade union laws of the 1980s will not be repealed - there will be no return to no-ballot strikes, flying pickets or secondary action or any of the rest of it". But Labour will attack the next wave of Tory employment laws as a step too far.
Last night, Labour reinforced that message at its gala dinner in London. "We have changed. And it simply defies logic to think that we would go through such radical change in creating new Labour, merely to slip back if we win."
Describing himself as an "eternal warrior" against complacency, Mr Blair told colleagues not to take victory for granted. And he assured businessmen at the dinner that Labour would not go "back to the old ways" in government.
Meanwhile, Mr Lang yesterday wrote to the European Social Affairs Commissioner, Padraig Flynn, to protest against a threat to tighten the EU rules on redundancy, following the decision by Renault to close its plant in Belgium.
Mr Flynn attacked the threatened closure and told the European Parliament that there was a balance to be struck between companies' economic needs and the rights of the workers.
But in a clear appeal to Tory Euro-sceptics, Mr Lang attacked the plan to extend workers' rights. "It is in the interests of all of us in Europe that you look for ways to remove restrictions on employment, rather than to increase them," Mr Lang said.