Tactical triumph

David Cameron’s announcement of his “Carlisle principle” (your report, 20 April) is an example of politics at its lowest ebb. He is clearly just playing the numbers game by giving up on the possibility of a single MP from Scotland in order to try to curry favour with voters south of the Border. Whether this has any effect in England remains to be seen, but I suspect and hope that reaction from potential Conservative voters in Scotland will see this blatantly cynical ploy backfire spectacularly.

There is evidence to suggest that 40 per cent or more of Scottish Tory voters are already considering voting tactically in order to support the strongest unionist party in their constituency.

This – combined with the fact that a huge number of voters are undecided – could result in a considerably more successful outcome for Labour than the polls are suggesting.

Colin Hamilton

Braid Hills Avenue

Edinburgh

Tactical voting would not be necessary if the UK had a more democratic electoral system which allowed voters to state first and second preferences. Then someone who had to choose between SNP and Green, or between Conservative and Ukip, could put their first preference first, knowing that their expression of a second preference would prevent their vote from letting in a candidate or party which they dislike more.

David Stevenson

Blacket Place

Edinburgh

Any supporters of either Labour or the Conservatives who have the misfortune to live in a constituency currently represented by a Liberal Democrat might ask themselves, before they vote for a party they do not support, what the consequences of that act might be.

The Liberal Democrats have just finished five years in coalition with the Conservatives. But now they say they do not rule out a coalition this time with ­Labour. So a vote for the Lib Dems seems to be a bit of a blind auction.

Peter Craigie

East London Street

Edinburgh

If it is only fair to England for prime minister David Cameron to adopt his Carlisle Principle to safeguard Holyrood harming England, it would surely be fair also to have a Dumfries ­Principle to protect Scotland from harm from Westminster. And could that please have retrospective effect?

Douglas R Mayer

Currie

Midlothian

A few short months ago David Cameron begged supporters of the SNP to stay with the Union. Now he views the prospect of the SNP contributing meaningfully to the Westminster system as “frightening”.

So what contribution does Mr Cameron deem acceptable? The weekly antics at Prime Minister’s Questions and Scottish Questions might provide an answer.

When Angus Robertson asks for reassurances concerning closures of Moray airbases, he is told “the only thing flying in an independent Scotland would be a kite”.

A week or two later a Tory with similar concerns over RAF Marham is treated to a considered and courteous reply.

It would seem for Unionists that, ideally, the role of the SNP in Westminster is to supply a small number of members who can be subjected to the sneers and jibes of Tory Toffs and Labour’s Dinosaurs.

Archie Davidson

Caroline Terrace

Edinburgh