Labour's Jeremy Corbyn will insist now is not the time to "retreat, run away or give up'' despite the party suffering a humiliating by-election defeat.
The under-fire leader will say he "cannot lie and say the result in Copeland was what we wanted'', but will also insist the ``time has come'' for his left-wing policies.
The Tories seized the Cumbrian seat from Labour in a dramatic victory on Thursday, with the result marking the first gain for a governing party in a by-election since 1982.
The loss of Copeland shows the 2scale of how hard our task is to persuade people of our message'', Mr Corbyn will say, as he addresses activists at the Scottish Labour Party conference in Perth.
There he will stress that Labour is "committed to fixing our rigged economy'' and to ``tackling the underfunding crisis in the NHS and in social care''.
He will argue this ``redistribution of power and wealth'' offers Scots more opportunities than independence but will also warn if Scotland ``pulls away from the UK'' it will hinder efforts to tackle inequality.
Mr Corbyn will say: "The policies and ideas we are setting out are policies whose time has come.
"But to win that fight we need to remain united. United in our belief in our movement. United in our commitment to once again make our society fairer, better and more just.
"That's why Labour believes that together we're stronger. Unity is still our strength.
"The scale of how hard our task is to persuade people of our message was underlined just this week in Copeland.
"Whilst we stood up to hatred and division in Stoke, I cannot lie and say the result in Copeland was what we wanted.
"But now is not the time to retreat, to run away or to give up.''
He will challenge Scottish First Minister Nicola Sturgeon to ditch talk of a second independence referendum, urging her to ``listen to the people and respect democracy''.
The Labour leader will insist: "The Scottish people are telling you to get on with your day job. And start fixing the mess you have made.''
He will tell party members that he looks forward to working with Scottish Labour leader Kezia Dugdale on plans for a People's Constitutional Convention and a more federal UK.
He will also stress that the problems facing the working classes are the same on both sides of the border.
Mr Corbyn will argue: "Class, not identity, is what still impacts most on people. It's the class that they are born into that impacts on their life chances.
"If you look at Nicola Sturgeon's constituency in Glasgow and mine in London, you'll see many of the same problems. Unemployment and poor housing, poverty pay and exploitative private landlords.
"What's required for the people of Blackburn, West Lothian or Lancashire, is a challenge to the power wielded, unaccountably, by big business and high finance. Independence doesn't offer that.
"It is the rigged economic system we need to challenge.
"If Scotland pulls away from the UK we will weaken our ability to challenge that system that creates the inequality and poverty in Islington, in Govanhill and countless places across Britain.''
He will go on to say: "I accept that many Scots feel let down and left behind.
"But we are committed to the redistribution of power and wealth in a way that no other party will ever even think of let alone achieve.
"We are committed to fixing our rigged economy.
"We are committed to tackling the underfunding crisis in the NHS and in social care. We are committed to education for all no matter their parents income and background
"We are committed to helping - not punishing - people who find themselves in difficulties and in poverty.
"We are committed to ending the punitive sanctions regime and ensuring there are no more I Daniel Blake's.
"We are committed to ending the obscenity of poverty and hunger in Britain in the 21st century.
"We are committed to making sure there is no need for food banks and charity to feed and look after millions of our people.
"We are committed to tackling the worrying rise in racism and xenophobia and will always remind people that a society should always be judged on how it looks after and cares for desperate people and refugees not how it shuts the door on them.
"We would never shut the door on poor innocent, unaccompanied children fleeing war and persecution.
"But that's what the Tories have just done. Shame on them.''