Media playback is unsupported on your device Media caption Ken Clarke: "We have got to refute some of the sillier things that are being attributed to our presence in the EU"

Pro-Europeans have got to "organise themselves properly" to defeat the "silly" arguments for leaving the EU, former Conservative Chancellor Ken Clarke has said.

Mr Clarke told the BBC there was a "real risk" of a UK exit from the EU.

Prime Minister David Cameron wants to change the terms of the UK's EU membership before an in/out referendum by 2017 if he wins the next election.

Labour says a referendum would present an unnecessary risk to the economy.

With some recent polls indicating support for leaving the EU, Mr Clarke - who left the government in July's reshuffle - said the political debate over the past six months had been "disastrous".

"We would diminish this country if we had a silly debate about Europe," he told BBC One's Andrew Marr Show.

'Hysterical'

Last month Mr Cameron said he would "rule nothing out" if other EU leaders would not agree to his proposed curbs on migrants' welfare payments.

Under his plans, migrants would have to wait four years for certain benefits.

The prime minister is under pressure to find a way to reduce the scale of migration from inside the European Union.

Ministers say the number of arrivals from the EU has "blown off course" their target to cut net migration to the tens of thousands by the general election.

The UK Independence Party, to which two Conservative MPs have defected this year, says the only way to control immigration is to quit the EU.

Mr Clarke said: "It's very difficult to debate immigration, which is why I do agree that the major parties have tended slightly to avoid it, because it runs away, it becomes almost hysterical quite rapidly in the public debate."

'Snap shots'

Legal immigration was "a feature of the modern world" although it had to be controlled, he added.

Mr Clarke also warned of "isolation" if Britain left the EU.

"Influence matters because a government has got to influence affairs in the greater world in order to look after the interests of its citizens," he added.

"Pro-Europeans have got to organise themselves properly... and refute some of the sillier things that are being attributed to our presence in the European Union."

Speaking on the same programme, former Labour cabinet minister Lord Mandelson dismissed the "snap shots" of recent polls and said more people were moving to the pro-EU cause the more they heard of the debate.