The House of Lords has been warned that it would be “ignoring” the wishes of ordinary people if it blocks a referendum on Britain’s membership of the EU.
Peers are debating the Conservatives’ bid to lay down in law a public vote on membership.
James Wharton, the Tory MP for Stockton South who steered the Bill through the Commons, said: “It is extremely important that the House of Lords recognise that this Bill, which has been passed through every stage of the democratically-elected House of Commons, needs to pass in order to give the British people a say on this very important issue.
"It would be strange indeed for the unelected House of Lords to block a Bill which is to legislate for a referendum.”
Voting against the referendum would put peers in a “very difficult position”, he added.
Speaking in the debate, former Thatcher minister Lord Crickhowell said: “Are we to add to the despair that exists about the political system?
“Are we going to block the wishes of ordinary people who want certainty that their views will be heard?"
The legislation would make a much discussed “in-out referendum” possible in 2017, although the result would not have to be legally binding.
But David Cameron has come under fire from critics for pandering to eurosceptics within the Conservatives and the rising pressure from UKIP.
Former Labour leader Lord Kinnock said: "To the detriment of our country he has pranced to their rhythm.”
He argued the referendum could cause “potentially huge” risks and costs for a government yet to be elected.
Lord Hannay of Chiswick claimed 2017 was a flawed time for the vote, clashing with Britain's presidency of the EU and French and German elections.
Labour’s Lord Mandelson said leaving Europe would “simply create more alienation and disillusion” among the public and that reform in Brussels was a better solution.
He added: “Having been a member of the European Commission, I think I can talk with some experience about the need for change in the European Union.”
UKIP peer Lord Willoughby de Broke urged the Lords to support the referendum to “throw off the shackles of the EU and to be a truly free nation”.
It is customary in the House of Lords for Bills agreed by MPs to be given a second reading and amendments at this stage are rare.
It must next go through the committee, report and third reading stages before going back to MPs.
Additional reporting by Press Association