Ed Miliband has insisted that Labour will defeat the Tories at the next general election in a bid to stem a flow of Labour voters planning to vote for Scottish independence to avoid further Conservative rule.

The Labour leader said the UK "was just one Christmas away from having a Labour government which can take up the cudgels of social justice on behalf of the people of Scotland and of the UK".

Miliband will stage a full Labour shadow cabinet meeting in Glasgow on Friday, and then host a Q&A session with undecided voters in Motherwell, as he attempts to re-energise his party's faltering campaign against independence.

Speaking on BBC Radio Scotland, he sought to quash the case put by the Scottish first minister, Alex Salmond and the pro-independence movement that Scotland and the rest of UK was now living a new era of Tory dominance, even though the Tories were roundly rejected by Scottish voters.

"Isn't it interesting that the nationalists have to pump up the idea of a Tory government to make their case?" Miliband said. He said Labour's cabinet meeting in Glasgow was part of the party's preparations for May's general elections, which he was confident Labour would win.

"This is a beatable Tory government," Miliband said. "To listen to Alex Salmond, he would suggest that there's a Tory hegemony across the United Kingdom. There isn't. The Tories haven't won a majority in 22 years across the United Kingdom. This is a Tory party, I believe, which had its high watermark at the last general election."

Miliband also confirmed that a future Labour government would block Salmond's bid to create a sterling currency union after independence, a position shared by all three of the main Westminster parties which came under severe strain when a UK minister said such a stance was a short-term campaigning position which would be abandoned after a yes vote.

Asked whether Labour would refuse to agree to a currency pact, Miliband said "correct".

He added: "All the lessons of the eurozone tell us if you're going to have a currency union, you also need to have a fiscal union that we [already] have across the United Kingdom and that is the sensible economic choice. This isn't about the politics. This is about the sensible economic choice and that is why I'm very clear about that."

In advance of his visit, Salmond's Scottish National party challenged Miliband to rule out suggestions from other senior Labour figures that a Labour government would scrap the Barnett formula, which sets spending for devolved governments, if Scotland votes to remain part of the UK.

The SNP claimed that Owen Smith, the shadow Welsh secretary, who is in Glasgow for the shadow cabinet, had backed calls from the first minister of Wales and Welsh Labour leader, Carwyn Jones, for it to scrapped or substantially reformed, potentially cutting Scotland's grant by £4bn.

Sandra White, an SNP MSP, said: "Ed Miliband must use his daytrip to Scotland to rule out the £4bn cut to the Scottish budget which is being proposed by senior members of his party – which would have absolutely devastating consequences for communities across Scotland already suffering under Westminster's austerity agenda."

Miliband is set to promise strict controls on zero-hours contracts across the UK later on Friday, as he seeks to warn the Scots that independence might force Scotland to compete with England by becoming a low tax, low-regulation economy.

He will unveil the findings of a party-commissioned review into such contracts by Norman Pickavance, a former director of human resources at Morrisons. The Labour leader's aides draw parallels with the way in which the Irish economy has tried to compete with the UK through low regulation and low taxes.

Most of the Pickavance proposals are expected to mirror suggestions made by the shadow business secretary, Chuka Umunna, including a commitment to give many workers on zero-hours contracts the right to a contract with fixed minimum hours.

Miliband will warn that if nationalists succeed in breaking up the UK, Scotland will join David Cameron in a race to the bottom on tax breaks and lower living standards for everyone else. Miliband will claim independence would make it more difficult to impose controls on zero-hours contracts on both sides of the border.

He will warn: "If we had a border running between Scotland and the rest of the UK, governments on both sides of it would be under intense pressure from powerful interests to undercut the other by lowering tax rates for the richest or worsen wages and conditions for everyone else."

• This article was amended on 28 April 2014 to correct a pronoun in a quote from Ed Miliband.