Labour peer Lord Rea has taken the unusual step of trying to block government legislation for NHS reform after it had already passed the Commons, as the Health and Social Care Bill began its consideration at second reading in the Lords on 11 October 2011.
Lord Rea, a former GP, has tabled an amendment that would stop the bill from passing at second reading - effectively killing it off.
Lord Rea argued that the bill was an "enormous" piece of legislation aimed at "top-down" reorganisation of the NHS which had not appeared in the Conservatives' manifesto or the coalition agreement.
Convention dictates that peers should not block any legislation that is a manifesto commitment.
Although debate in the chamber usually kicks off at 2.30pm on a Tuesday, Lords business managers agreed to an early start to accommodate the large number of peers hoping to make their views on the legislation clear.
100 peers have have requested the chance to speak during the Lords second reading debate and they are set to vote on 12 October.
The bill, which contains the government's health service reform plans in England, was sent back for a second committee stage in July after the government made a series of changes following widespread anger among NHS professionals and patient groups.
The changes include adding hospital doctors and nurses to the new commissioning consortia - not just GPs, as proposed by the original bill - and scrapping an April 2013 deadline for the new boards to take over.
It is believed some senior Liberal Democrats want more changes to the proposed reforms before they will support them.
Two crossbench peers, Lords Owen and Lord Hennessey, have tabled an amendment calling for part of the bill to be sent to a special select committee which allows witnesses to give evidence and will scrutinize the bill further.
They say the bill raises serious constitutional issues, particularly aspects relating to the role of the health secretary in overseeing the NHS and the role of a new body, Monitor, in promoting competition within it.
Labour has said it will support the amendment.
Unions are opposed to plans to open up the health service to greater competition from the private sector, claiming it will lead to the privatisation of the NHS.
Health Secretary Andrew Lansley has dismissed the claims as "ludicrous scaremongering".
The government says reform is necessary to safeguard the future of the NHS, but Labour claims the plans are ''high-cost and high-risk''.
part two of the Health and Social Care Bill from day one.
part three of the Health and Social Care Bill from day one.
part four of the Health and Social Care Bill from day one.