LONDON (AP) _ Declaring ``treason,'' a duke's son jumped on the speaker's historic seat in the House of Lords on Tuesday, as scions of Britain's noblest families began a final debate on ending their right to sit and vote in Britain's unelected upper chamber.

``Behind this bill for Lords' reform lies a hidden agenda which is treason,'' the Earl of Burford said before leaping on the Woolsack, a square seat of stuffed wool that has been reserved for speakers since the 14th century.

Deputy Speaker Lord Boston, who was perched on the Woolsack, ducked out of the way as ushers grabbed and ousted the 34-year-old earl, heir to the 14th Duke of St. Albans.

Burford's protest in the normally placid, well-mannered chamber marked a stormy start to the debate on the final stage of Prime Minister Tony Blair's Labor government bill to remove hereditary peers from the Lords.

Britain's opposition Conservative Party _ which most of the 759 bluebloods in the 1,213-member chamber support _ grumbled until the last minute about their lordships having to vote themselves out of existence.

But the hereditary peers were expected to go along with their fate.

If the Lords rejected the bill, Blair could present it again in the Labor-dominated House of Commons in the new parliamentary session starting Nov. 17. The Lords cannot twice reject a bill passed by the Commons.

Burford was exercising the right of the eldest sons of peers to sit on the steps of Queen Elizabeth II's throne, but not take part in proceedings.

But the earl _ whose family motto is ``A pledge of better times'' _ sprang up from the steps, complaining volubly that the bill removed ``inalienable rights granted to my family by King Charles II in 1684.''

``Indeed the very existence of the monarchy is threatened,'' he said.

The Blair government has not decided on the composition of a new House of Lords, which is expected to be partly appointed and partly elected. Critics charge that the new chamber will be a gathering of governing party members and cronies of the prime minister.

Until the new chamber is set up, the current ``life peers'' _ mainly former members of the Commons and others appointed for life _ will sit with 92 of the hereditary peers.

Those hereditary peers will be selected by ballots among their fellow aristocrats. Final results will be announced Nov. 5.

The bill will only end the 800-year right of hereditary peers to be lawmakers. They retain their titles and estates.