The flag over Downing Street during the 2006 World Cup
The flag of St George will fly over Downing Street on Wednesday, to mark St George's Day.
All UK government buildings with two flag poles are being encouraged to fly the English national flag, alongside the union flag.
It follows a review of flag flying practices. Number 10 will in future fly the Scottish and Welsh flags on their patron saints' days.
The English flag was flown over Number Ten during the 2006 football World Cup.
Prime Minister Gordon Brown is encouraging all government buildings with two poles to fly the St George's flag on Wednesday.
Those with only one pole should fly the union flag, which has precedence over national flags.
The prime minister's spokesman confirmed that the Scottish Saltire and Welsh dragon would be flown on the relevant saints' days.
But as Northern Ireland does not have an official national flag, one would not be flown on St Patrick's Day.
The spokesman added: "The prime minister's view is that of course we should celebrate our Britishness, but celebrating our Britishness does not mean we cannot also celebrate our Englishness, Scottishness, Welshness or Northern Irishness."