A YouGov poll yesterday put Ukip on 10% support across Scotland, a point ahead of the Greens on 9%.
Four years ago, under the proportional voting system for Euro elections, the SNP won two Euro seats, Labour two, the LibDems one and the Conservatives one.
Voters next go to the polls in May. Scottish Greens leader Patrick Harvie said: "The winning post for this election will be about 10%, and with the Greens and Ukip neck and neck, the first to that line is likely to shut out the other. By voting Green in this election, Scots have the opportunity to make this the one place where Ukip falters."
The poll showed Labour on 39%, the SNP 22%, the Tories 13% and the LibDems on 5%.