SIR Alex Ferguson has donated £501 to the pro-UK Better Together campaign, reigniting a bitter row over referendum funding limits.

The Manchester Utd boss's gift was £1 above the pro-indepedence Yes Scotland campaign's self-imposed £500 cap on donations from outwith Scotland – a limit they have urged their opponents to adopt.

He accused First Minister Alex Salmond of trying to silence England-based Scots who wanted their views on independence to be heard.

Mr Ferguson, a lifelong Labour supporter, said: "Scots living outside Scotland but inside the UK might not a get a vote in the referendum but we have a voice and we care deeply about our country.

"It is quite wrong of the man who is leader of Scotland to try and silence people like this."

The gesture came as the chief executive of Better Together, Blair McDougall, stepped up pressure on the SNP Government to accept higher campaign spending limits in the crucial four month period before the vote.

Ministers want spending by Yes Scotland and Better Together capped at £750,000 during the final run-in, well below the £1.5 million limit tentatively suggested by the Electoral Commission.

Mr McDougall said the Government's proposed limit was a fix to stifle debate. He warned it could "undermine confidence in the result," raising the possibility of a legal challenge.

A SNP spokesman said: "The No campaign wants to spend a silly amount of cash. It can only be because they are so bereft of volunteers to knock on doors for free they want to bombard voters with unsolicited mail and phone calls."

The Electoral Commission will offer its advice on campaign spending limits and the referendum wording question next year.

Ministers have warned they might disregard the impartial watchdog.

Meanwhile, the SNP welcomed backing for independence from the Master of the Queen's Music, Sir Peter Maxwell Davies who said at the weekend that he had undergone a slow and gradual and thoughtful conversion to the cause.

SNP Westminster leader Angus Robertson said: "The Yes campaign for an independent Scotland is attracting support from across society, and Sir Peter Maxwell Davies's backing is extremely welcome."