Westminster has paid tribute to Princess Margaret who died on Saturday.

Speaking at the end of his Africa trip, the prime minister praised her "sense of service'' and the work she had done for many good causes.

"The thing that people understand about the royal family is the sense of service that they have,'' Tony Blair told Sky News.

"Princess Margaret had it. Before she was ill she did an enormous amount of public service, of charity work. They work, actually, very hard for us, the Royal Family, and the single common theme that I think runs throughout their lives is this idea that they owe a duty of service to the people they lead. I know from the conversations I had with her she felt that deeply too," he said.

"It is a difficult life for them and they have to live in a way that is completely different from other people. They do have a very, very strong sense of duty and I think by and large people are grateful for what they do. I know certainly through the dealings I have had with the Royal Family as prime minister, I found that the single most unifying theme in the lives of the Queen, the Queen Mother, Princess Margaret, the whole of the Royal Family.''

Leader of the Opposition, Iain Duncan Smith said the princess was respected across the globe.

"It is with great sadness that we have learned today of the death of Her Royal Highness Princess Margaret. Her loss will be felt not just throughout the United Kingdom but also the Commonwealth and the wider world where she was held in the greatest affection," he said.

"Princess Margaret devoted much of her life to public duty and her charitable work. She was patron or president of more than 80 charitable organisations many of which were concerned with caring for the young and for the sick. We remember too her great love for and encouragement of music and the arts, especially her beloved ballet. Her loss will be particularly felt in this Jubilee year."

Liberal Democrat leader Charles Kennedy added his tribute.

"I was very sad to hear of the death of Princess Margaret. We all suffer when we lose a close relative. I send the Queen, Queen Mother and the Royal Family my greatest sympathy," he said.