Image copyright Charles McQuillan Image caption Nigel Dodds at the launch of the DUP election manifesto in April

David Cameron risks losing the support of Northern Ireland's Democratic Unionists over the Tories' handling of Scotland.

In a letter to the Guardian, Nigel Dodds said that the Tories were in danger of "abusing" the House of Commons over Scotland.

He said he was both "alarmed" and "concerned" about the election campaign in England.

He also warned about the risk of fuelling "nationalist paranoia".

Mr Dodds' comments in a letter published in the Guardian on Monday, could affect the prime minister's hopes of remaining in office.

A recent YouGov/Sunday Times poll suggests Mr Cameron would need DUP support to stay in Downing Street.

The DUP could hold an influential number of votes if the general election results in a hung parliament.

Mr Dodds, who was leader of the DUP group in the last parliament, has already outlined demands from a potential government partner and has not ruled out working with Labour or the Conservative Party.

In his letter, Mr Dodds said the UK needed "responsible politicians", adding that "the current state of the campaign greatly concerns me".

He said the SNP was his first concern.

"In a hung parliament, regardless of ideology, these are not politicians set on stability and good government," he wrote.

Nevertheless, he defended the right of Scots to vote in the Commons.

"That's why we fought and won the referendum: to enshrine the rights of Scots to go on sending representatives, fully equal to every other, to Westminster," he said.

"Glib and lazy talk about SNP MPs somehow not being as entitled to vote in every division in the Commons as any other British MP, simply fuels nationalist paranoia".

Mr Dodds was highly critical of Tory moves to build up the SNP as a way of damaging the Labour party in Scotland.

In his letter, his focus was on the Conservative Party's tactics, particularly the idea of offering English votes for English laws, (Evel).

He claimed that using William Hague to "drum up support for Evel" was "not just a flawed political tactic, it's also a constitutional mess".

Mr Dodds said the House of Commons could not 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 England's real needs," he said.

Nigel Dodds is a candidate for Belfast North. Also standing in the constituency are Fra Hughes, Independent; Gerry Kelly, Sinn Fein; Alban Maginness, SDLP; Jason O'Neill, Alliance Party and Gemma Weir, Workers Party.

Mr Dodds' party is defending eight seats in Northern Ireland. It hopes to recapture Belfast East, the seat formerly held by DUP leader and first minister Peter Robinson for 31 years, up to 2010.