Labour peers have been accused of trying to sabotage a bill which would result in the redrawing of constituency boundaries and a reduction in the number of MPs. The House of Lords has been sitting overnight and tempers have flared.

Labour objects to the speed with which the legislation passed in the Commons and wants the various proposals to be debated separately.

Is it a watershed moment for the upper chamber and will it set the tone for the coalition's period in government? We get an expert guide to what's happening from Professor Vernon Bogdanor of Brasenose College, Oxford (David Cameron's former tutor and author of a forthcoming book on the coalition).

Also on the panel this week we have the Guardian's Polly Toynbee and the Observer's Nick Cohen. They discuss whether MPs should be allowed to use Twitter inside the Commons chamber. Polly is a recent convert (@PollyToynbee) while Nick has left Twitter to concentrate on a new book.

Also this week: as health secretary Andrew Lansley announces sweeping reforms of the National Health Service, we debate whether the government has a mandate for such a serious overhaul that was neither in the Conservatives' manifesto nor the coalition agreement.

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