Unpeer

[…] to destroy the king and parliament; disinherit his royal posterity; unpeer all the lords, and level them with the dust; […]

Source: wiktionary

[…] not that he thought it a degradation for peers to sit in the House of Commons, but it was a degradation to the peers of Scotland to give them liberty to unpeer themselves, and to descend from the order to which they belonged.

Source: wiktionary

When the Earl of Selborne died, who as Sir Roundell Palmer had been made Lord Chancellor, his son, a prominent M.P., declared he would not go to the Upper House, that he would unpeer himself.

Source: wiktionary