Jeremy Corbyn has come across as a man of the people and real leader.
The General Election could determine if the United Kingdom continues to exist, Kezia Dugdale warned, as she urged people in Scotland to reject the nationalist politics offered by the SNP and the Conservatives.
Labour said it would improve "engagement and dialogue" with the devolved administrations and would seek to ensure the final Brexit deal addressed "specific concerns".
In a bid presumably to complete her crushing of Ukip, the manifesto will say: "When immigration is too fast and too high, it is hard to build a cohesive society" and that with annual net migration last recorded at 273,000 "immigration to Britain is still too high".More news: London City Airport's flights to be controlled from 70 miles away
But Len McCluskey, the leader of the country's biggest trade union says he is confident the opinion polls will start to change in Labour's favour.
"We can not allow this to be the choice at this election - because it doesn't represent what the vast majority of people in this country want".
The party said it accepts last year's referendum result for Britain to withdraw from the EU but it would scrap May's negotiating position, prioritizing continued access to the single market and customs union.
Asked what success would look like in Scotland where Labour had just one MP, Ms Dugdale said: "I am not going to put a number on it because I haven't produced a list of target seats".More news: Trump knew Flynn was under investigation weeks before inauguration
Both Gordon Brown and Ed Miliband resigned after leading Labour to defeats in 2010 and 2015 but, amid speculation that jockeying for position has already begun, there have been suggestions that Mr Corbyn could stay on if he equals the 30.4% vote share that Ed Miliband got in 2015.
A Conservative spokesman said: "Jeremy Corbyn can't deliver any of this - it just doesn't add up".
Labour spending plans would open up a £58 billion "black hole" in the public finances, leading to higher taxes and more debt borrowing, the Conservatives have warned. "While his figures are a fantasy, it is ordinary working families who will pay".
It insists they are fully costed and will be fully covered by tax rises, including increasing corporation tax from 19% to 26% and raising the top rate of tax for earnings above £80,000 to 45p and to 50p for income over £123,000.More news: Erdogan Supporters in Violent Clash with Protesters in Washington
Labour has also said it would return the railways to public ownership as franchises expire, or in some cases using franchise reviews or break clauses.
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