Prime Minister Gordon Brown pledged today to do "whatever is necessary" to preserve the United Kingdom in face of demands for Scottish independence.

In an interview with the Sunday Telegraph, Prime Minister Brown called for pro-union parties to join with business groups and trade unions to campaign against a break-up of the UK.

"Some issues are bigger than party politics and need to be addressed in the common interest," he told the newspaper.

"I will do whatever is necessary to ensure the stability and maintenance of the Union."

His intervention follows a bruising row over the government's position on whether to support a referendum on Scottish independence.

Scottish Labour leader Wendy Alexander caused consternation in Westminster and Holyrood earlier this week when she called for an immediate referendum on independence, having previously said such a poll was unnecessary.

She said the move was intended to expose the "hollowness" of the position of Alex Salmond's Scottish National Party administration which has promised a referendum but not until 2010.

Prime Minister Brown defended Alexander as an "excellent leader" of Labour in Scotland but distanced himself from her call, saying he was personally "not persuaded" of the case for a referendum.

Support in Scotland for independence after 300 years of union with England varies from poll to poll.

A YouGov poll last weekend gave a figure of 19 per cent in favour but other analysts have put support at up to one third in the nation of just over five million people.

International Development Secretary Douglas Alexander, brother of the Scottish Labour leader, told BBC television his sister had "called the SNP's bluff". But he said he was "not convinced" now was the right time to hold a referendum.