If Tony Blair presses ahead with a general election on May 3, he faces a battle royal in the House of Lords to salvage the health and social care bill - the legislation he introduced to implement and advertise the government's NHS reform plan.

The bill completed its committee stage in the upper house last Thursday with only minor amendments to the most controversial clauses. Its report stage - the last opportunity for peers to force changes on key proposals such as abolition of community health councils (CHCs) and eligibility for free nursing care - is due on Thursday next week.

But the last date for Blair to brush aside concern about the foot and mouth crisis and plump for a May 3 election is next Tuesday. If he takes the plunge, the health bill will enter the uncertain "wash-up" procedure that decides what happens to uncompleted business before parliament is dissolved.

There are two main options. The government could subject the bill to a "strike-out" procedure, allowing the enactment of clauses that are not contested. For this to be effective, there would have to be horse trading with the opposition parties, letting all sides claim some influence on the outcome.

But if a prospective deal was not to ministers' liking, the government could decide to allow the bill to fall, and return with something similar after the election, assuming that Labour wins.

Earl Howe, the peer leading for the Conservatives on the bill, says the Tories would "play hard to get" during the pre-dissolution negotiations. They would not object to uncontroversial measures such as pilot schemes for pharmacy services. But they would be likely to put up stiff resistance to abolition of the CHCs and would probably refuse to go along with the government's "stingy" definition of free nursing care and with the clauses allowing the release of confidential patient records.

Lord Clement Jones, for the Liberal Democrats, says the government would be facing two or three defeats at report stage and ministers could not insist on getting everything through unscathed under pressure of dissolution. "I expect the government to be content to let it drop and bring back a number two bill [a repeat measure] after the election," he says.

A senior government source dismisses that idea. "We want the bill done and dusted during the wash-up," he says. "It's more likely that we'd manage to get an agreement in the upper house - probably requiring concessions on our part as well as theirs - than that we'd use the Parliament Act to force this through in the next parliament."

Tory and Lib Dem peers would be asked to decide whether they wanted Labour to go into the election blaming the opposition for blocking free nursing care in nursing homes that had been due for implementation in the autumn before the cold weather comes.