Gordon Brown yesterday declared he had abolished the "ridiculous rule" that bans flying the Union flag on government buildings other than on certain days of the year and revealed he would be spending his summer holiday in Scotland and England.

Yesterday, the UK symbol of red, white and blue was flapping above No 10. However, The Herald has learned that the rule the Prime Minister so disparaged does not exist, and in Scotland there is special dispensation to fly the Saltire from government buildings.

Mr Brown, who has frequently extolled Britishness, told GMTV: "When I came in to be Prime Minister, I was looking at all the rules that exist. We had a very strange rule for decades that said you can't fly the Union Jack more than 18 days a year.

"It was because they listed the number of public events and on no other days would the Union Jack be flown. We thought it was a ridiculous rule. We've got rid of the rule and it will be up to public offices to decide if they want to fly the flag."

He added: "People are very proud of the symbols of what it is to be British. The monarchy, parliament, all great institutions including the NHS."

However, the Department for Culture, Media and Sport (DCMS), whose responsibilities include official flag-flying, gave a different picture.

A spokeswoman explained that, barring such incidents as deaths in the Royal family, there were 17 days when the Union flag should be flown on all government buildings across the UK. These include the birthdays of members of the Royal family, Commonwealth Day on March 12, Coronation Day on June 2 and the Queen's Wedding Day on November 20.

However, the spokeswoman stressed that a government building could fly the Union flag or another national flag on any other day but the relevant department had to apply for permission from the DCMS, which, in turn, had to get permission from the Queen - as the buildings belong to Her Majesty's government.

The spokeswoman also noted how the Union flag should also be flown from all government buildings on national days, ie St David's Day, in the respective nations of the UK.

However, Scotland is a special case. On the 18 nominated "flag days" north of the border the Saltire can be flown. If a Scottish government building had two flagpoles then both the Saltire and the Union flag could be flown but the former should "never be flown in a superior position" to the latter.

Last night, The Herald learned that Jack Straw, Westminster's Justice Secretary in charge of constitutional issues, had been in contact with Alex Salmond. A spokesman for the First Minister said: "The tradition is that it is the flag of Scotland that's flown on government buildings in Scotland. We are comfortable with the flag arrangement at present and we believe the Westminster government is equally comfortable with it."

Elsewhere, on BBC TV, Mr Brown noticeably broke with Mr Blair's tradition of holidaying abroad in grand surroundings, revealing he would be spending his in Britain. He said: "We have got two very young children and I'm looking forward to a relatively quiet holiday at home, part of it in England, part of it in Scotland." Just where was not disclosed.