Cameron and Cable clash over EU referendum vote
Vince Cable has dismissed calls for an "in-out" referendum on the UK's membership of the European Union as a "serious distraction".
Speaking at the launch of a campaign to increase the scope of the single market, the business secretary said a public vote would add to uncertainty.
But Prime Minister David Cameron urged the Liberal Democrats and Labour to "get off the fence" over Europe.
The House of Commons will vote on an EU Referendum Bill on Friday.
Mr Cameron has promised to hold a referendum on the UK's membership of the EU by the end of 2017 if the Conservatives win a majority at the 2015 general election.
This would follow a renegotiation of the UK's relationship with Brussels.
Mr Cameron's party is backing Tory MP James Wharton's private member's bill at its second reading stage on Friday, but it is not supported by the Liberal Democrats or Labour.'Turn up and vote'
Most Lib Dem and Labour MPs are not expected to turn up to the debate. This means the bill is likely to pass its first parliamentary test easily, although it will face far greater opposition at later stages.
Mr Cameron, who has faced pressure from Conservative MPs to hold a referendum, urged the other parties to "get off the fence and say what they think about it".
Speaking on a trip to Kazakhstan, he said: "I totally support it. It is my policy written into law. And I would say to all MPs, turn up and vote."
But, asked about the referendum vote at a meeting in central London organised by the Business for New Europe group, Mr Cable said: "It's a distraction. It's a serious distraction. We are recovering from the worst economic crisis for the best part of a century.
"The last thing we need now is massive levels of uncertainty in the business community."
Mr Cable said the current policy of not holding an EU referendum unless there was a "fundamental change" in the UK's relationship with Brussels was a "perfectly sensible position that's clearly understood and we are sticking with that".
The Business for New Europe (BNE) group wants the European single market to extend further into digital, energy, transport and telecoms markets, while focusing the EU's efforts on achieving trade deals with major economies such as the US and Japan.
Deputy Prime Minister Nick Clegg, who is also Mr Cable's party leader, said: "The Liberal Democrats have been consistent throughout. The Conservatives have changed.
"They now want to pluck a slightly arbitrary date in the diary out of thin air to have a referendum on a very ill-defined process of so-called renegotiation."'Great dangers'
On the same day as the BNE's campaign launch, the rival Business for Britain group announced a cross-party initiative aimed at securing a referendum.
Businessman and Labour donor John Mills said public opinion had become "more Eurosceptic than before".
He added: "Our own estimates are that half the shadow cabinet are worried about Labour going into the next election without a commitment to hold a referendum.
"There are great dangers with the Labour Party going into the next election without a commitment to holding a referendum, [which] would do very little to enhance the chances of there being a Labour government."
Mr Wharton, the MP for Stockton South, said it should be "relatively straightforward" for his bill to progress on Friday, as Tory MPs backed it "to a man".
He added: "The Labour Party en masse isn't going to turn up, and the Liberal Democrats will take the same route. In the longer run, we need to build up a stronger base of support."
He said that, given the limited amount of parliamentary time for private members' bills, there was more danger from other MPs trying to delay its progress at the next - committee - stage, or trying to insert amendments before the bill can gain its third reading.
If it got past these stages, it was uncertain how the House of Lords would vote, Mr Wharton said.
Eurosceptic Mr Wharton topped a ballot of backbenchers in May which allows him to introduce his own legislation. Downing Street has said Conservative MPs will be under a three-line whip, the strongest order a party can give, to support it.
For Labour, shadow foreign secretary Douglas Alexander said: "Any decision about Britain's place in Europe should be judged on what's in our national interest.
"Sadly, we have a prime minister who seems to think the priority when it come to Europe is keeping his party in line, rather than getting the country on track.
"This private member's bill is just the latest attempt by David Cameron to keep his restive backbenchers in line."