Prime Minister David Cameron pays tribute to Queen Elizabeth II

(CBS/AP) Prime Minister David Cameron said at Parliament Wednesday that Britain should pay tribute to Queen Eliabeth II's "unerring grace, dignity and decency" as she marks 60 years on the throne.

Pictures: Pageantry in London
Pictures: Queen Elizabeth II
Pictures: Prince Harry kicks off Diamond Jubilee tour

"Around the world dictatorships have died and democracies have been born, and across the old British empire a vibrant Commonwealth of nations has expanded and flourished," Cameron told legislators. "Throughout this extraordinary change, the longest monarch in our history has remained resolutely unchanged in her commitment and studious in her duties."

The Diamond Jubilee weekend will be held June 2-5, with the main highlight likely to be a huge pageant on the River Thames, in addition to a gala concert. Festivities are also taking place across Britain, in the country's 14 overseas dependencies and in 15 far-flung nations where the queen is also head of state. Already, Prince Harry has launched events in the Caribbean.

Cameron told the House of Commons that the queen had offered a stability which is "essential for our national life."

"The nation holds her in its heart, not just as the figurehead of an institution, but as an individual who has served this country with unerring grace, dignity and decency," he said.

In deciding to televise her annual Christmas message from 1957, open up her palaces to visitors and host summer garden parties, the queen had "ended a thousand year distance that existed between British monarchs and their people," Cameron said.

The queen and her husband Prince Philip, also known as the Duke of Edinburgh, will tour Britain from now to July.

Cameron said the monarch had traveled more widely than any head of state in history, meeting at least 4 million people on her visits. "She has been heard to say," he quipped. "I have to be seen to be believed."