Mr Balls appeared to take a harder line on the issue than Ed Miliband, who has refused to rule out the prospect of an arrangement that could see the SNP propping up a minority Labour government in exchange for concessions.
A spokesman for Mr Miliband last night refused to say whether the shadow chancellor’s views reflected those of the leader and would only say that the party was “fighting for a majority” and to win outright in May.
First Minister Nicola Sturgeon has insisted that the SNP would not help sustain a Conservative government in power, but indicated the party could be prepared to support Labour in some Commons votes as part of a confidence and supply arrangement.
Nationalist leaders last night hit back at Mr Balls and said most Scots “would not forgive” Labour if the party allowed David Cameron to remain in power because of its hostility to the SNP and a refusal to agree an anti-Conservative pact.
The hardening of the shadow chancellor’s stance on SNP cooperation came as polls showed the Nationalists poised to make sweeping gains from Labour in May.
Mr Balls was asked whether he would consider a deal with the Nationalists, who would press Labour for the removal of Trident from Faslane and a more radical extension of devolution, as part of the price for SNP support in Commons votes.
The shadow chancellor, when asked on Sky News whether he would consider a deal with the SNP if the election on 7 May produced an indecisive result, replied: “No.”
Mr Balls said: “I don’t think anybody is suggesting any suggestion of a deal with the SNP at all – we’re fighting hard for a majority.”
With opinion polls suggesting the SNP could make major gains in Scotland, and Labour and Conservatives running neck-and-neck in national surveys, many observers believe that Mr Miliband may need support from the Nationalists to form a government.
Mr Miliband repeatedly said earlier this month that he was “not about deals and coalitions” when he was asked about possible co-operation between Labour and SNP at Westminster.
However, the Labour leader would only state that he was focused on his party “winning a majority government”, and pointedly failed to rule out an arrangement with the SNP.
The intervention from Mr Balls suggests the party’s leadership could face splits over potential co-operation with the SNP, although Mr Milband would be expected to have the final say.
A spokesman for Mr Miliband last night refused to comment on the remarks from Mr Balls, but insisted the party leader was firm on the issue.
Mr Miliband’s spokesman said: “The position has not changed. We are fighting for a Labour overall majority. We are campaigning for an overall majority.”
However, SNP Westminster leader Angus Robertson said Mr Balls’ remarks showed the shadow chancellor had not noticed the Nationalists’ surge in the polls.
Mr Robertson said: “Ed Balls seems oblivious to polls that show that the people of Scotland want to see the SNP holding the balance of power at Westminster with a minority Labour government – and people in Scotland would not forgive Labour if they refused to work with the SNP and ushered in another five years of Tory government.
Mr Balls’ remarks came after the Prime Minister said a deal between Labour and the SNP would be “genuinely frightening”.
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