Ed Miliband accused the pro-independence campaign of “ugly” tactics after campaigners hurled abuse at him in chaotic scenes during a visit to Edinburgh.
The Labour leader was branded an “absolute liar” by protesters when he toured the St James Shopping Centre in what was supposed to be a trip to persuade undecided voters in the final stages of the referendum battle.
Shoppers were trampled and pushed aside as campaigners from both the Yes and the No camps clashed during the walkabout.
Mr Miliband struggled to speak to voters amid the frenzy and the visit was quickly brought to an end.
Among the few members of the public he was able to chat to, one was a visitor to the city and the other declared themselves a Yes supporter.
Mr Miliband told the BBC: “I think we have seen in parts of this campaign an ugly side to it from the Yes campaign.
“I think debates should be conducted in a civilised way, I think that’s very, very important, but I understand that passions run high.
“What I’ve enjoyed about this campaign, including today when I get the chance, is meeting people who are genuinely undecided.”
Mr Miliband had intended to use the visit to tell voters that more powers would be transferred to Scotland in the event of a No vote.
He told reporters: “If people vote No, it’s for change and more powers for a stronger Scotland, as well as NHS funding guarantees, and that’s got to be weighed against the big risks of voting Yes.
“That has been the choice that people are facing in these last couple of days in this referendum campaign.”
He added: “I think that the momentum is with the No campaign as people recognise that there is a clear offer of change by voting No.”
In a statement released ahead of the visit the Labour leader had insisted the desire for political change had been heard in Westminster and would be delivered.
He promised that “things will not go back to the way things were” after Thursday and called on Scots to help lead reform of the British state.
“On the other path of Yes is a future of separation and risk, an irreversible decision, a risk to jobs, the economy and the NHS, as we abandon the shared resources and redistribution of our United Kingdom,” he said.
“With a No vote, things will not go back to the way things were after Thursday.
“Scotland has shown why we must and why we will change our whole country. Scotland can lead that change across Britain.
“A vote for No is a vote for change. Let’s take our chance to change our country together.”