David Cameron arrived in Scotland to do battle with Gordon Brown, as the election campaign was overshadowed by the de-selection of a Labour candidate.The Tory leader said he had been backed by more than 50 Scots businesses, while the Prime Minister was expected to attack his rival's spending policies.
Labour's Moray candidate was suspended for making offensive remarks about rivals on his Twitter internet page.
The Lib Dems campaigned on fisheries jobs and the SNP on election debates.
Mr Cameron, campaigning in Aberdeen, said his business backers, including the maker of Tunnock's tea cakes, were supporting his campaign against Labour's planned 1% National Insurance rise.
The increase, which Mr Cameron has pledged to cancel for most workers by funding it through efficiency savings, has become a key election issue.
Mr Cameron denied Scotland would be disproportionately affected by his party's plans to cut public spending, telling the BBC: "The aim is to increase employment in Scotland, to increase economic growth in Scotland.
"We won't do that if we go on wasting money in the public sector and putting up taxes which is going to hamper the recovery."
The Tories also want to increase their number of Scottish MPs from one to 11 on the 6 May election.
Mr Cameron, who toured construction firm Stewart Milne Group in Aberdeen, said of the target: "I won't make predictions, I will just do my very best to make sure the number goes up and up."
He was accompanied on the visit by Alex Johnstone, the Tory candidate for the West Aberdeenshire and Kincardine seat which the party would need a swing of nearly 9% to take from Liberal Democrat Sir Robert Smith.
Meanwhile, Mr Brown is using a speech later to step up his attack on Tory claims that £6bn of efficiency savings could fund reversing the bulk of the planned increases.
Earlier, Scottish secretary Jim Murphy unveiled Labour's Scottish campaign poster on the eve of the Grand National, depicting the election as a "two horse race" between Labour and Tories.
"People have a clear choice between the Tories, who would choke off the economic recovery, or Labour, who will nurture the economy back to full health," said Mr Murphy.
Labour's day of campaigning was overshadowed by the Twitter row, which resulted in the party saying Stuart MacLennan would no longer be the party's candidate in Moray, after he admitted tweeting offensive comments.
Scottish Liberal Democrat leader and Tavish Scott visited a seafood processing plant in Eyemouth, Berwickshire.
He said small communities needed sustainable jobs, which were best delivered by cooperation between the two parliaments.

Mr Scott added: "Scotland's fishing and processing industries don't need a Labour government in Westminster fighting with an SNP government in Holyrood.
"While they turn inwards Liberal Democrats are looking outwards to create sustainable jobs and businesses that serve Scotland and the world.
"That's the change we offer."
Scottish First Minister Alex Salmond revealed he was taking part in a Scottish election debate hosted by Sky TV.
Speaking on a visit to the company's call centre in Livingston, he said Scotland had "largely been cut out of the picture" when it came to TV election debates.
"Sky have been the most accommodating of all the broadcasters and have shown themselves willing to engage with the SNP from the start," said the SNP leader.
"That is in stark contrast to the attitude of the other main broadcasters, who have colluded in a carve-up with the London parties to shut Scotland and Wales out of the leaders' debates."This article is from the BBC News website. ? British Broadcasting Corporation, The BBC is not responsible for the content of external internet sites.
Labour's Moray candidate was suspended for making offensive remarks about rivals on his Twitter internet page.
The Lib Dems campaigned on fisheries jobs and the SNP on election debates.
Mr Cameron, campaigning in Aberdeen, said his business backers, including the maker of Tunnock's tea cakes, were supporting his campaign against Labour's planned 1% National Insurance rise.
The increase, which Mr Cameron has pledged to cancel for most workers by funding it through efficiency savings, has become a key election issue.
Mr Cameron denied Scotland would be disproportionately affected by his party's plans to cut public spending, telling the BBC: "The aim is to increase employment in Scotland, to increase economic growth in Scotland.
"We won't do that if we go on wasting money in the public sector and putting up taxes which is going to hamper the recovery." The Tories also want to increase their number of Scottish MPs from one to 11 on the 6 May election.
Mr Cameron, who toured construction firm Stewart Milne Group in Aberdeen, said of the target: "I won't make predictions, I will just do my very best to make sure the number goes up and up."
He was accompanied on the visit by Alex Johnstone, the Tory candidate for the West Aberdeenshire and Kincardine seat which the party would need a swing of nearly 9% to take from Liberal Democrat Sir Robert Smith.
Meanwhile, Mr Brown is using a speech later to step up his attack on Tory claims that £6bn of efficiency savings could fund reversing the bulk of the planned increases.
Earlier, Scottish secretary Jim Murphy unveiled Labour's Scottish campaign poster on the eve of the Grand National, depicting the election as a "two horse race" between Labour and Tories.
"People have a clear choice between the Tories, who would choke off the economic recovery, or Labour, who will nurture the economy back to full health," said Mr Murphy.
Labour's day of campaigning was overshadowed by the Twitter row, which resulted in the party saying Stuart MacLennan would no longer be the party's candidate in Moray, after he admitted tweeting offensive comments.
Scottish Liberal Democrat leader and Tavish Scott visited a seafood processing plant in Eyemouth, Berwickshire.
He said small communities needed sustainable jobs, which were best delivered by cooperation between the two parliaments.

Mr Scott added: "Scotland's fishing and processing industries don't need a Labour government in Westminster fighting with an SNP government in Holyrood. "While they turn inwards Liberal Democrats are looking outwards to create sustainable jobs and businesses that serve Scotland and the world.
"That's the change we offer."
Scottish First Minister Alex Salmond revealed he was taking part in a Scottish election debate hosted by Sky TV.
Speaking on a visit to the company's call centre in Livingston, he said Scotland had "largely been cut out of the picture" when it came to TV election debates.
"Sky have been the most accommodating of all the broadcasters and have shown themselves willing to engage with the SNP from the start," said the SNP leader.
"That is in stark contrast to the attitude of the other main broadcasters, who have colluded in a carve-up with the London parties to shut Scotland and Wales out of the leaders' debates."This article is from the BBC News website. ? British Broadcasting Corporation, The BBC is not responsible for the content of external internet sites.

