tory peer and former minister lord forsyth warns against snp attacks .
he says the talking up the snp threat undermines future of the uk .
comes as john major warns a labour-snp alliance will cause chaos .
he said labour propped up by snp would mean high taxes and fewer jobs .
a comres poll for itv news last night found the majority of the british public -- 54 per cent -- do not want miss sturgeon to play a role in the next government . some 59 per cent do not want the snp involved at all .