Media playback is unsupported on your device Media caption David Cameron tells the BBC that immigration is important and plans will be set out "in due course"

David Cameron has said action is needed to curb EU immigration and pledged to have "one last go" at negotiating a better deal for the UK in Europe.

Speaking in Kent, where there is a by-election next month, he said: "We need further action to make sure we have more effective control of migration."

Last week the Conservatives lost a by-election to the UK Independence Party, which wants the UK to leave the EU.

Lib Dem Nick Clegg accused the Tories of "blind panic" at UKIP's rise.

Labour accused Mr Cameron of making "vague promises" and said it would "examine any real proposals the government comes forward with".

'Radical'

UKIP leader Nigel Farage said: "It is impossible to change the free movement of peoples within Europe without a fundamental treaty change with 27 other European countries.

"Nobody wants it, nobody is interested, and the prime minister knows it's not possible."

According to The Times Mr Cameron has promised backbench Conservative MPs a "game-changing" announcement on immigration, which would "almost certainly" come before Christmas.

Image copyright PA Image caption Douglas Carswell became the first elected UKIP MP in the Clacton by-election

Some Conservative MPs are understood to be pushing for the announcement to be made before the Rochester and Strood by-election, triggered by the defection of Conservative MP Mark Reckless to UKIP, on 20 November, at which immigration is expected to be a major factor.

Among the "radical" options being considered by the government is an "emergency brake" on immigration from some EU countries, according to the Times.

The Sun newspaper goes further, saying Mr Cameron will "demand the right to limit European immigration" as the "price of staying in the EU".

Analysis - by Chris Mason

Perhaps never before has muscular, even if a bit vague, sounding stuff on immigration been quite the political virility symbol it is today.

David Cameron is basically saying: "We get it and we'll do big things to address it." But, when pressed for detail, he uses phrases like "in due course".

Which basically means: "Err, hang on a minute."

The central question is this: can big changes on European immigration rules be done while staying in the EU?

Yes, hint the Conservatives. No says UKIP. Possibly, but let's stop being shouty, say the others.

Meanwhile, a chunk of north Kent is currently absorbing the biggest wave of immigration it's ever seen, as trainloads of politicians roll up with leaflets, smiles and handshakes.

The Rochester and Strood by election is 35 days away - and the Conservatives, UKIP, Labour, Lib Dems, the Greens and others are all buffing themselves up for it.

But it says details of the proposed restrictions - which could involve caps on arrivals from certain countries or an "Australian-style" points system operating within the EU - have yet to be finalised.

At the moment the European Union has freedom of movement rules, which means everyone can move to live - and in most cases have the right to work - in any member state.

Asked about the newspaper reports on his weekly LBC radio phone-in, Mr Clegg said: "The Conservative Party is in such a blind panic, a complete flap, about UKIP that every day I wake up to new headlines.

"No Conservative has ever put any proposal to me. They have never breathed a word of it government. Who knows? Maybe the press briefing they issue tomorrow will be different."

The deputy prime minister added: "I think the Conservative Party have got a fundamental problem. They are running after UKIP in a complete panic."

'Increased numbers'

For Labour, shadow immigration minister David Hanson said: "We will examine any real proposals the government comes forward with to manage immigration with interest.

"We do need reforms to the free movement rules - which is why Labour has already put forward practical plans to stop people travelling to claim benefits, deport people who commit crimes, and stop employers undercutting local jobs and wages with cheap migrant labour. We want to see fair movement not free movement.

"But instead of practical plans, David Cameron is briefing vague promises to stave off panic and revolt from his Eurosceptic backbenchers when instead real action is required."

Mr Cameron is under pressure from Conservative MPs to set out details of his strategy for renegotiating the relationship with Brussels ahead of a promised 2017 in/out referendum if the party remains in power after next year's general election.

Image copyright EPA Image caption The Conservatives hope to bounce back from Clacton defeat top victory in Rochester

In his speech to the Conservative Party conference, Mr Cameron said numbers had "increased faster than we in this country wanted… at a level that was too much for our communities, for our labour markets. All of this has to change - and it will be at the very heart of my renegotiation strategy for Europe.

"Britain, I know you want this sorted so I will go to Brussels, I will not take no for an answer and when it comes to free movement - I will get what Britain needs."

But Mr Cameron has declined to state whether he would be prepared to back a British exit if he does not get the concessions he wants, insisting he is confident of success in the negotiations.

It is unclear whether it would be possible for the EU's freedom of movement rules, seen as a fundamental part of the union, to be changed as Mr Cameron hopes.

European Commission spokeswoman Chantal Hughes said: "Free movement of workers is a fundamental principle in the EU. It's enshrined in the treaty. It constitutes also an essential part of the single market.

"All we've seen are vague reports... were we to receive such details, concrete measures, from the UK government, of course we would assess them to ensure their full compliance with European rules."

She added that a series of bilateral deals between the UK and other EU members could contravene free of movement and "would obviously not be acceptable".

Mats Persson, director of Open Europe, a think tank that calls for reform of the EU, told that any attempt to secure "some sort of mechanism" that would allow Britain to curb its number of immigrants from the EU would be "very, very difficult" to achieve.