UKIP has seized on new immigration figures published as voters went to the polls in a European election contest dominated by the immigration issue.
The party predicted its support would be boosted by official statistics showing net migration to the UK rose to 212,000 last year, up from 177,000 the previous year.
Politicians on all sides have urged voters to reject the Eurosceptic party, amid signs it could make a breakthrough in Scotland.
The Herald revealed this week a new survey showed seven in 10 Scots back stricter immigration controls, a key plank of Ukip policy.
SNP leader Alex Salmond said yesterday only his party could stop Ukip, adding that the elections were an important moment to determine "the kind of Scotland we want to live in".
David Coburn, Ukip's lead candidate in Scotland, hit back at the SNP and its candidate Tasmina Ahmed-Sheikh, previously a member of the Conservatives.
"She doesn't let her principles get in the way of her ambition, so people are not going to vote for her," he predicted.
Labour attacked both parties, saying voters should not let the the SNP "use this election as a launchpad for separation in September".
With less than a year to go, the European Parliament vote will also be viewed by some as a dress rehearsal for the next general election, but early indications yesterday suggested that turnout across Scotland could be low.
Glasgow City Council said just that by mid-afternoon 16% of its voters had cast their ballots,
The new immigration figures show David Cameron is now highly unlikely to meet his target to cut immigrant numbers to the tens of thousands by next year.
Ukip leader Nigel Farage said the Prime Minister had broken a "solemn promise" to the British people and urged voters to protest by voting Ukip. Mr Farage's party is fighting for the sixth and final European Parliament seat in Scotland.
The spot is currently held by the Liberal Democrats who are bracing themselves for a disaster that could see them lose all their 12 UK MEPs. A leaked internal memo showed senior LibDem figures have been briefed to blame the losses on the "electoral cycle".
Labour is also feeling the pressure, with former Northern Ireland Secretary Peter Hain among senior Labour MPs warning the party has failed to counter the Ukip threat.
The Tories have insisted a vote for them is one for reform of the European Union.
Mr Farage said he was "reasonably" confident of his party's chances, but was forced to deny claims Ukip is racist after days of damaging headlines.
He said: "Twenty minutes ago the immigration figures were out. 526,000 people settled in this country last year. It's just impossible. We cannot go on with numbers like that."
Labour sources said the party hoped to gain up to nine MEPs, and could also gain 200 councillors in English council elections, which took place yesterday.
The party says it has been "ruthlessly" putting resources into seats it will be targeting in next year's general election.
The Liberals are predicting a mauling in the council elections and say their hopes lie with strongholds where they currently have MPs.
The council election results, announced tomorrow, could serve as warm-up for the European election tally.
Counting for the European Parliament seats will not start until Sunday and there will be no announcements until after 10pm when the final polling booth closes across Europe.
Final results in Scotland will not be available until Monday morning as there will be no Sunday counting in the Western Isles.
In 2009 Labour and the SNP took two Scottish European Parliament seats each, with the Tories and Liberal Democrats returning one each.
The results will be on herald scotland.com on Sunday night.