Nicola Sturgeon: UK 'needs an overhaul'
The SNP could help overhaul the UK's "crumbling" institutions, Scotland's first minister has said.
Nicola Sturgeon told students at the London School of Economics that her party could work to bring "positive change across the UK".
Recent polls have led to speculation that the SNP could hold the balance of power following May's election.
But Labour leader Ed Miliband has ruled out a formal coalition with the SNP.
Speaking shortly after Ms Sturgeon's speech, Mr Miliband also said there would be "no SNP ministers" in any government he leads.
He said: "There are big differences between us on a whole range of issues, not just on the integrity of the UK and another referendum but on fair funding between the countries of the UK and fair taxes.
"In repeating this claim, the Conservatives and David Cameron are simply trying to scare people. Labour will not go into coalition with the SNP."
However, Mr Miliband has not ruled out some sort of post-election deal with the SNP, although Labour has previously downplayed speculation that it could enter an informal "confidence and supply" arrangement with the SNP if there was no outright winner in the general election.
Ms Sturgeon's speech at the London School of Economics on Monday morning set out her approach to tax and spend in areas such as Trident nuclear weapons, the North Sea oil and gas industry and the work allowance.
The speech, which came ahead of Wednesday's budget, also contained a pledge that the SNP would serve not only Scotland's interests, but those of the whole of the UK.
Ms Sturgeon's speech came as a new study suggested a majority of people in the UK believe Scotland will become an independent country despite the "No" vote in last year's referendum.
Researchers at the University of Edinburgh said 69% of people in Scotland believed there would be a split, while 59% of those surveyed in England, 54% in Wales and 59% in Northern Ireland thought that Scotland would eventually leave the UK.
The findings were from a survey of more than 7,000 voters across Britain.
In her speech, Ms Sturgeon argued that the UK's most powerful institutions were crumbling and needed urgent reform, and said the SNP could help to overhaul them.
And she said the UK Parliament's "arcane" processes and headline-grabbing surprises "often limit debate on genuinely complex issues".
She said: "The Palace of Westminster is in such a dilapidated condition. Its fabric is crumbling, some areas are prone to flooding and other parts haven't been properly refurbished for generations.
"It's not just the building that needs to be overhauled. It's the institutions."
The first minister also said: "The process UK governments follow now allows virtually no time for proper deliberation or consultation.
"That problem is made worse by the way in which successive governments have approached the Budget.
"Chancellors take pride in pulling rabbits out of the hat. Surprises are seen as a virtue. They help to create headlines and wrong-foot the opposition.
"It's much more difficult for that to happen in Scotland. The Scottish government has to publish a detailed draft budget each September, four months before the budget bill is laid before parliament."
Ms Sturgeon acknowledged that "none of this is easy" and that "neither my party or my government has all of the answers, far from it, but we know we need to try and we do want to be part of that effort."
And she pledged: "If we get the opportunity we intend to be constructive voice in the months and years ahead. We won't just serve Scotland's interests, although we will most certainly do that.
"But we will seek to do more than that if we get the opportunity, we will also seek to play our part in bringing about positive, long lasting and progressive change right across the UK."
This was Ms Sturgeon's second high-profile speech in London in recent weeks.
Last month at University College London she attacked the "austerity economics" of the main Westminster parties and called for an extra £180m in public funding to be made available.
Responding to the speech, Scottish Liberal Democrat leader Willie Rennie said it was "farcical" for the first minister to claim that the SNP would bring positive change for the whole UK.
He said: "It is farcical to suggest a party which is sworn to break up the UK would be capable of bringing positive change for the UK.
"If the first minister's idea of positive change is breaking NHS waiting time targets, increasing school class sizes and misjudgements on the economy then I suspect people will reject her plans."