Jeremy Corbyn would make repealing "vicious" trade union legislation brought in by the Tories one of his first acts if Labour wins the general election.
The Labour leader will make the pledge as he addresses trade union members in Scotland, insisting his party will "never, ever apologise" for its close ties to the unions.
While Labour are trailing well behind the Conservatives in the polls, Mr Corbyn will make clear he is campaigning to win the June 8 election.
And if he becomes the next prime minister, one of his first acts will be to repeal the Trade Union Act brought in by David Cameron.
Amongst other measures, the controversial legislation introduced a threshold for workers voting in strike ballots for action to be legal.
A Labour government under Mr Corbyn would also carry out an inquiry into the practice of blacklisting, and into the "Battle of Orgreave" in the miners' strike, where striking workers clashed with the police.
The Scottish Government would also be urged to set up its own inquiry into the actions of the police in Scotland during the bitter dispute.
Mr Corbyn, who will address the Scottish Trades Union Congress in Aviemore, will say: "Labour will never, ever apologise for the closeness of our relationship with the trade union movement, you are our family.
"That is why one of the very first things we will do when forming our Labour Government will be to repeal the vicious Tory Trade Union Act. Giving working people the rights to collectively organise and make their lives better, safer and more content.
"We will open inquiries into blacklisting and Orgreave. And we urge the Scottish Government to set up an inquiry into the actions of the Scottish police during the miners' strike."
A Labour government would "challenge the rigged system that is holding our country back" and would "stand for the many not the few".
Mr Corbyn will add: "While the timing of the election was unexpected, the choice is clear and the stakes are high. Let no-one be in any doubt, we are in this election to win it and we will fight for every seat in every corner of these isles.
"The choice facing the country is clear. It's the people versus the powerful."
Labour is also promising workers a "real living wage of £10 an hour" by 2020 and to end the cap on public sector pay.
Mr Corbyn will also vow: "We will end the need for food banks.
"We will upgrade our economy to create wealth for all through investment in our infrastructure, helping our small businesses, delivering high skill jobs and ending poverty pay.
"We will put conditions on the massive public spending budget with private business to ensure no company wins a public contract if they avoid or evade taxes, don't pay their local suppliers on time, or don't recognise trade unions.
"We will never put tax giveaways to corporations and the wealthiest above our vital public services like our social care system and NHS. And we will give schools and colleges, those engines of opportunity, the funding they need.
"Only Labour will negotiate a Brexit deal which protects the interests of working people.
"Labour's Brexit deal will build on the rights won for workers, consumers and the environment in the EU. We will put jobs and living standards first.
"That's why Labour is campaigning to win every seat across the whole country."
Labour currently has just one MP in Scotland following the 2015 general election, when an SNP tsunami saw the party win all but three of the 59 Scottish seats up for grabs.
A Panelbase poll for the Sunday Times in Scotland put support for Labour on 13%, compared to 33% for the Conservatives and 44% for Nicola Sturgeon's SNP.
Scottish Conservative deputy leader Jackson Carlaw branded the Labour leader a "clear and present danger to the Union".
Mr Carlaw said: "This is a man who didn't even campaign in Scotland to fight for the Union in 2014 because he was 'doing stuff' in London.
"It's the same man who, since becoming leader, has talked up a pact with the SNP and just last month, said he was 'absolutely fine' with a second referendum.
"It all points to one clear fact: Mr Corbyn would sell pro-UK Scots down the river in a heartbeat.
"Nicola Sturgeon is trying to use this election to push ever harder for a second referendum on independence. Under Jeremy Corbyn, Labour would simply roll over and let her do so."