David Cameron risks losing the support of the DUP over the Tories' attitude to Scotland.
In a letter to the Guardian, Nigel Dodds said that the Tories were in danger of "abusing" the House of Commons over Scotland.
Mr Dodds said he felt the Tories' English manifesto, launched last week by David Cameron and William Hague, was "fuelling nationalist paranoia".
He also called for tactical voting by pro-Union voters in Scotland, urging them to vote for the "unionist candidate best placed to win their seat" regardless of which party they represent.
He said of the SNP: "In a hung parliament, regardless of ideology, these are not the politicians set on stability and good government. Yet whatever those of us who believe in the continuation of the UK as a pluralist, multi-national state might think, we mustn't allow ourselves to be provoked into behaving the same way. And this is where the campaign south of the border has so alarmed me."
Referring to the Tories' English Votes for English Laws plan as Evel, Mr Dodds added: "It's not just a flawed political tactic, it's also a constitutional mess. The Commons can't be used as a part-time English assembly. It's the union parliament and abusing it in this way wouldn't and couldn't answer the very real needs England has.
"For far too long now we have blundered into unthought-out, one-sided constitutional change. This fatal habit has to end. Evel unfortunately, would simply be more of the same."
Launching the proposal last week, the Prime Minister said it was "simply unfair" that Scottish MPs would soon be able to vote on English income tax when English MPs could not reciprocate due to devolution.
"English Votes for English Laws is not about fragmenting the UK," he said. "It's not about division and difference and pulling apart, it is about making our United Kingdom stronger.
"Because if you have basic constitutional unfairness like we've had, if you have the people in one part of the UK feeling like they are getting a raw deal, then resentment festers and that undermines the bonds and the fellow-feeling that are the basis of the United Kingdom."
People are older in East Antrim. The coastal constituency has a much higher median age (40) compared to the overall average (between 32-35) of the others, with 15% of the total population retired. Only North Down is older (42).