A bill that would allow a referendum on the UK's membership of the EU in 2017 has cleared its first Lords hurdle.

But Tory former Lords leader Lord Strathclyde warned peers that delaying its passage in subsequent stages would be "comprehensively damaging" for the upper chamber's reputation.

The private member's bill would enact PM David Cameron's pledge to hold an in/out referendum in 2017.

Labour warns of a possible "devastating economic effect" if it becomes law.

Conservative backbencher James Wharton stewarded the legislation successfully through its Commons stages, despite Labour and Lib Dem efforts to delay its passage, but it is likely to face a tougher time in the House of Lords.

This bill is a pig in a poke and it cannot be in the national interest to buy into it Labour's Lord Liddle

Peers approved the bill at second reading, the parliamentary stage at which MPs or peers consider the general principles of the legislation, without a vote, after a debate lasting nearly seven hours.

The bill now proceeds to more detailed scrutiny, when Labour, Lib Dem and pro-EU Conservatives are expected to join forces to try to amend the bill.

If amended, the legislation would need to clear the Commons again by the end of February or it will again face the risk of running out of parliamentary time.

'Whispers'

The overwhelming assumption at Westminster is that the bill will probably not make it out of the Lords alive

If this bill fails, the government could take the unusual step of re-introducing an identical bill and using the Parliament Act - a piece of legislation which enables the Commons to over-rule the Lords - to force it on to the statute book.

But despite David Cameron's backing for the bill - part of efforts to prove he is serious about holding a referendum - he may opt not to take such a step.

Even if the bill successfully becomes law it does not guarantee a referendum in 2017 since no Parliament can bind its successor.

Speaking in Friday's debate, Lord Strathclyde said: "We do have the power to block the bill but I believe we do not have the authority to do so.

Image caption Lord Strathclyde was a Conservative frontbencher for 25 years

"Nobody outside this House would understand why the Lords were deliberately denying the people their say on this issue.

"I hear it whispered that a small number of peers plan to stop the bill, to use our much valued free and open procedures to disrupt progress, and therefore delay the bill, and therefore use time to stop it from becoming law.

"I can think of little else that would be so comprehensively damaging to the well-earned reputation of the Lords for fair-minded scrutiny."

'Coward's way out'

Lord Dobbs, the Conservative peer who is spearheading the bill's passage through the Lords, earlier told Radio 4's Today programme that Europe had become a "pestilence in our political system" and "we need to get rid of this burden".

Media playback is unsupported on your device Media caption Lord Dobbs: Europe has become a poison in our political system

"Nobody below the age of 60 has ever had a chance to have a say on this issue," he said.

"We need to decide one way or another whether we are going to stick with Europe or leave."

Opening debate in the upper chamber, he added: "This bill is needed and it is very much wanted."

But Labour frontbencher Lord Liddle argued: "We all know this is not really a private member's bill - it is a Conservative bill, it is a party bill, full of Conservative Party purpose.

"That purpose is to try and create a semblance of unity in a party that is deeply divided on the question of the European Union and at the same time to convince voters tempted by UKIP not to follow down that path."

Four hundred and fifty six years ago this week, Britain lost its last foothold on the European continent after the siege of Calais. The Queen said that when she died they would find 'Calais' engraved on her heart. My Lords, when my time has come they might well open me up and find this bill engraved on my heart. Lord Dobbs, Conservative peer

He added: "If the business world was to think seriously that this Bill had the slightest chance of passage and that the Conservatives were likely winners of the next general election, the uncertainty generated over our continuing membership of the EU for the next four years could have a devastating economic effect."

Labour peer and former European Commissioner Lord Mandelson accused the Conservatives of "grandstanding" to UKIP while Lib Dem peer Lord Oakeshott said a referendum was "the coward's way out".

"They are an abdication of responsibility by leaders and parties who haven't the courage to take a decision," he said.

Ex-Labour leader Lord Kinnock argued that this bill only "exists because the prime minister, through a series of lame gestures and rejected assurances, has tried to assuage the militant Europhobes in his party and has failed".

"His efforts have been as fruitless as appeasement always deserves to be," he said.

But UKIP leader Nigel Farage said the two Labour former commissioners were not impartial participants in the debate, claiming they were contractually obliged not to criticise the EU.

"What justification is there in giving those in receipt of conditional EU pensions any credence at all on the subject?" he said.

"They should both declare the conflict of interest and step far away from the debate if they want the general public to have any faith at all in UK politics."

He also accused peers for "throwing spurious amendments at [the bill] to make it run out of parliamentary time".

Both the prime minister's deputy Nick Clegg and Labour leader Ed Miliband have warned of the uncertainty and damage to business they say would be caused by committing to a referendum in 2017.