The Conservatives and Liberal Democrats are dishonest and cannot be trusted to keep their promises or deliver more powers for Scotland, according to SNP leader Nicola Sturgeon.

Ms Sturgeon launched an attack on the coalition parties following the publication of a Tory manifesto yesterday which both the SNP and Labour deemed a betrayal of the Smith Commission on devolution, and a Lib Dem manifesto today which she said follows five years of austerity and "dishonesty".

The Scottish First Minister today visited the offices of children's charity Barnardo's in Kirkcaldy, Labour's safest Scottish seat held by former prime minister Gordon Brown until his retiral upon the dissolution of parliament.

Sporting a colour she described as "SNP red", Ms Sturgeon said she is the only leader proposing "responsible" spending increases in contrast to the continued austerity of her opponents.

She also attacked Tory Chancellor George Osborne, who is campaigning in Aberdeenshire today, and dismissed Labour shadow chancellor Ed Balls's insistence that he would reject any SNP demand that puts Scotland's interests over those of England.

"George Osborne's long-term economic plan is penalising the most vulnerable in our society," she said. "It has held back economic growth and it's undermining our public services, and only the SNP offers a clear alternative to austerity in this election.

"What the Tory manifesto proves is that the Tories can't be trusted to deliver more powers to the Scottish Parliament."

She added: "The Liberal Democrats have been part of a government with the Conservatives for the last five years that have imposed austerity cuts on the people of Scotland.

"The SNP is the only party offering spending increases in the next parliament, responsible increases that still allow us to cut the deficit but allow us to invest in things that matter to people the length and breadth of this country.

"For most people across the country the Lib Dems represent dishonesty - they broke their promise on tuition fees.

"They represent cuts - they helped the Tories impose painful austerity cuts.

"And they represent everything that has been wrong with the last Westminster government.

"The Liberal Democrats have been part and parcel of everything the Tory government has done and they will pay the price for that at the next election."

Commenting on Mr Balls's insistence that an unequal SNP deal would be "a betrayal of the English vote", Ms Sturgeon said: "If you vote for the SNP you will get MPs that will seek to build alliances with others with progressive policies for a strong voice for Scotland and better decisions coming out of Westminster.

"Labour and the Tories are both proposing austerity in the next parliament - I say that is wrong."

Ms Sturgeon said Barnardo's is a good example of the kind of service that the SNP is seeking to protect.

"In this election it's only the SNP that is offering a clear alternative to continued austerity," she said.