First Minister Nicola Sturgeon has branded the Trade Union Bill an attack on workers which should be dropped.
The proposed UK government bill, which would make it more difficult to call strikes, has drawn criticism from across the Holyrood chamber.
And Ms Sturgeon told the Unite union conference in Clydebank the plans would never have been raised in Scotland.
She said she would not let the Scottish government employ agency workers to undermine a strike in Scotland.
The Trade Union Bill would impose a minimum 50% turnout for ballots on industrial action - and public sector strikes would need the backing of at least 40% of those eligible to vote.
Ms Sturgeon told delegates at the conference that Holyrood had already shown "overwhelming opposition" to the measures, which are due to be debated by MSPs.
She said: "If the Tories have any respect whatsoever for the democratic process in Scotland they will drop this bill and they will drop it now
"It's a measure which I don't think would ever have been proposed, let alone passed, in the Scottish Parliament.
"The SNP doesn't just oppose this bill in Scotland, we oppose it right across the UK, we stand shoulder to shoulder with everybody and with anybody who opposes this bill, no matter where they are in the UK.
"And on this issue Labour shouldn't be attacking the SNP, and the SNP shouldn't be attacking Labour, we should be standing united.
"So we will oppose this bill across the UK, but we'll also argue for Scotland to be exempted from its provision, and let me be clear on this as well - if the bill becomes law we will not willingly or voluntarily co-operate with it or implement it in Scotland."
But Labour MSP Neil Findlay called the position "empty words", adding that when Labour wanted to challenge the competence of the bill at Holyrood the move was blocked.
Meanwhile, Unite's general Secretary Len McCluskey called on Scottish Labour to reconnect with Scotland.
Speaking on Sunday Politics Scotland, Mr McCluskey said the ideology of New Labour had pushed ordinary working class Scots towards the SNP.
He told the programme: "The reality is that we have to say to Scottish people that Labour is under new management and we're going to try to regain your trust, we're going to try to make certain that Labour once again is seen as on the side of ordinary working people.
"Because very evidently, over a long period of time, Scottish Labour lost that trust and it manifested itself on May the 7th last year in a way that was quite staggering."