Theresa May will vow never to allow the UK to become "looser and weaker'' in a speech ahead of a meeting in Scotland with Nicola Sturgeon.
3,400 Members Sign Up To Scottish Labour
Scottish Labour has attracted more than 3,400 new members since the general election.
The party now has more than 28,000 people in Scotland signed up to help its campaign, made up of more than 17,000 members, almost 3,300 registered supporters and almost 8,000 affiliated supporters.
Scottish Labour's new leader Kezia Dugdale said the new figures confirmed the party can be "a force for radical change''.
It comes after Labour lost all but one of its Scottish seats at Westminster in May's general election.
Ms Dugdale said: "This is exciting progress but we know there is a lot of work to be done before we regain the trust of the people of Scotland.
"I want thousands more people to get involved as we set about the work of transforming Labour so we can transform Scotland.
"The job for everybody in our movement - members, supporters, trade unionists and elected representatives - is to go out into communities across the country and tell people what our Labour values are.
"I want people across Scotland to be left in no doubt about what we stand for and who we stand with.
"We want a country where a person's ability to do well is determined by their potential, work ethic and ambition, not by their background. We stand with people who just want to get on in life.
"I don't ask people immediately for their vote but that they take a fresh look at Scottish Labour. We are changing.''
The SNP's James Dornan said the publication of Labour's membership numbers had "brought an end to the mystery'' surrounding the figures.
The MSP said: "With 15,000 members, the SNP's trade union group has almost as many members as Scottish Labour, and membership of the SNP as a whole is almost six times Labour's.
"While Labour worked hand in glove with the Tories during the referendum and failed to vote against the harshest of Tory cuts, the SNP is standing up for Scotland and leading the opposition to the Tory government at Westminster.
"With latest polls showing record support for the SNP, it is clear people in Scotland are continuing to put their trust in us as we approach next year's Scottish Parliament election.''
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