Sir Malcolm Bruce claimed voters were beginning to realise that Scotland could find itself outside government if it votes overwhelmingly for the SNP next month.
Although polls suggest a large influx of SNP MPs could hold the balance of power, both the Conservatives and Labour have ruled out a formal coalition with them.
David Cameron has ruled out any kind of deal, whereas Ed Miliband has repeatedly left the door open for SNP support on an informal issue-by-issue basis.
Despite opinion polls Nick Clegg’s Lib Dem party still believes it can win enough seats to do business with the Conservatives or Labour.
Bruce said: “I am meeting people who voted Yes, who are not voting for the SNP and feel it’s maybe gone too far and we should move on. Secondly there wasn’t a uniform vote across Scotland, there were very substantial variations.
“Here we are in the nort-east of Scotland, it was overwhelmingly against independence, certainly well over 60 per cent. Therefore you cannot assume that the SNP will actually get enough votes automa- tically to hold or win seats in the north-east or other parts of Scotland.
“We are finding that people are voting tactically because if you take these polls all the way through, Scotland could effectively put itself out of reach of being part of any government because we have elected nobody of the governing party, whatever it is. That’s not good for Scotland.”
Bruce is standing down as MP for Gordon, the Lib Dem-held seat that Alex Salmond is now favourite to win for the SNP.
In Cabinet minister Danny Alexander’s seat of Inverness, Nairn, Badenoch and Strathspey, the Lib Dems are writing to Conservative voters in an attempt to keep the SNP out. A Lib Dem letter sent to Conservative-supporting constituents quotes the Scottish Tory leader Ruth Davidson praising him.
The letter refers to an interview Davidson did on BBC Radio 4’s Today Programme when she said: “Fair play to the Liberal Democrats for stepping up . . . some Liberal Democrats like Danny Alexander did very, very well and I’m thankful to them for that.”
The letter signs off: “Remember the Conservatives cannot win this seat. Only Danny can keep the Nationalists out.”
Last night the Conservative candidate for Inverness, Nairn, Badenoch and Strathspey Edward Mountain said: “I think Desperate Dan is getting more desperate. There doesn’t seem to be much activity from the Labour Party up here, so it looks more and more as if this constituency will be a toss-up between the Conservatives and the Lib Dems over who is going to hold up against the Nationalist vote.’’
Campaigning in Bruce’s old seat with Alex Salmond, Nicola Sturgeon described the SNP as the national party of Scotland. “Polling shows that the SNP has become the national party of Scotland in all senses – leading in the polls across all areas and demographics of Scottish society,” she said. “Distrust in the Westminster establishment parties has grown – the Lib Dems leave a trail of broken promises behind them and Labour and the Tories are signed up to £30 billion spending cuts.”