ED Miliband joins the independence debate today arguing that staying in the UK is the best way to achieve the social justice dreamed of by late Labour leader John Smith.
The party's UK leader is due to speak at the Scottish conference in Perth today where the referendum will be the key focus.
It is the party's last conference before the poll in September and leaders will be outlining why they think Scotland should vote no.
Former Prime Minister Gordon Brown addressed a United With Labour event last night for party members explaining how he saw Scotland's future within the UK.
Today Mr Miliband is due to say the SNP would take Scotland on a race to the bottom competing with the UK to lower taxes for big business.
He will tell the delegates if elected to Downing Street next year he will implement the proposals of Johann Lamont's devolution commission which she revealed earlier this week, with more powers for the Scottish Parliament.
He is expected to say: "This is no ordinary time and no ordinary conference for reasons we all know because in 180 days Scotland will determine its future. It is Scotland's decision - and Scotland's alone.
"But everyone in this Labour Party knows we're better together.
"When we're in need, we don't ask whether we are Scottish, English, Welsh or Northern Irish, we look after each other.
"And, in the same way, we will build prosperity for the future and for every part of the United Kingdom in a race to the top by creating those good, high-paying jobs that people should expect."
The conference will be addressed by Johann Lamont tomorrow and Deputy Leader Anas Sarwar on Sunday.
The party still faces a struggle to win back support following a series of defeats at Holyrood and Westminster with crucial elections looming for Mr Miliband and Ms Lamont.
Following the independence referendum in September, next May Ed Miliband hopes to defeat David Cameron to become Prime Minister and in 2016 there will be elections in Scotland to the Scottish Parliament either under the current devolution system or to an independent country depending on the outcome in the referendum.
Mr Miliband is expected to remember former leader John Smith who died in 1994 and tell delegates a vote for the UK would carry on his principles.
He will say: "John Smith was a man who passionately believed in social justice.
"That flame of social justice still burns and we can honour his legacy by winning the fight for Scotland to remain in the United Kingdom."