Blair Jenkins, chief executive of pro-independence Yes Scotland, said with 100 days to go it is now reaching the "sharp end of the campaign".
He revealed his group has gathered 789,191 declarations from people who say they will back independence in the September vote.
Mr Jenkins said: ''I know there are many people who remain to be convinced and it is by talking with them in millions of conversations that we will win them over to Yes.
Loading article content
''Over the next 100 days I appeal to every single person who believes in Yes to make it their business to talk with and persuade those who remain undecided to come our way.''
He added: ''I think that the final part of the campaign is going to be about who gets the tone and the mood of the campaign right.
''I think a lot of this will come down to who people trust. Why would people trust David Cameron and George Osborne going forward any more than they have up until now?
''I think the issue of trust will be a big one as we move closer to the vote.''
He also dismissed claims that the unionist parties' promises of more powers would boost the No campaign.
Mr Jenkins said: ''What people have to be realistic about is what will the appetite be at Westminster seriously to push through further constitutional changes for Scotland after this referendum, and when you've got a very fully agenda.''