One of the first acts of a Labour government will be to repeal the “vicious” trade union legislation introduced last year, Jeremy Corbyn is set to announce as he unapologetically celebrates the party’s relationship with Britain’s unions.

In his first visit to Scotland during the 2017 general election, the Labour leader will also attempt to entice Scots back to his party, which suffered a catastrophic defeat at the last general election, losing 40 of its 41 seats in the region.

In a speech at the Scottish Trade Union Congress he will say that Labour “will never, ever apologise for the closeness of our relationship with the trade union movement”. Addressing delegates directly, he will say: “You are our family.”

Mr Corbyn will add: “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 people the rights to collectively organise and make their lives better, safer and more content.”

The legislation, brought in by David Cameron’s administration, introduced a threshold for workers voting in strike ballots for action to be legal. Among other measures it also requires strikers to give employers a minimum of 14 days’ notice before industrial action, rather than seven.

The Labour leader will also pledge that his party is campaigning to win every seat across the whole country. Should Mr Corbyn become Prime Minister, he will add, a Labour government would also carry out an inquiry into the practice of blacklisting, and into the “Battle of Orgreave” in the miners’ strike.

Speaking in Aviemore, he 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 will challenge the rigged system that is holding our country back. And just like trade unions, we will stand for the many not the few.”

But the Scottish Conservative leader Ruth Davidson said Mr Corbyn “couldn’t be bothered” to campaign during the independence referendum in Scotland in 2014 and “has said he would do a deal with the SNP”.

She added: “And the last time he was in Scotland he said he was ‘absolutely fine’ with a second referendum. On top of that, there’s no way he could get a good deal from the other European leaders.