David Cameron has insisted that his comments about Jo Cox have been intended purely as a tribute to the Labour MP, after Nigel Farage accused him of a "despicable" attempt to use her death to boost his chance of winning Thursday's EU referendum.

Speaking as MPs gathered in Westminster for a recall of Parliament to pay their respects to Mrs Cox, Mr Farage said the Remain campaign were "scared witless" about the prospect of defeat on June 23 and were trying to create a link in voters' minds between her killing and the EU vote.

The Ukip leader also dismissed the defection to the Remain camp of former Conservative chair Baroness Warsi as a "Number 10 put-up job".

Lady Warsi said her decision to change sides was sparked by a "xenophobic" poster released by Mr Farage, as well as "lies" from Michael Gove over the prospect of Turkey joining the EU.

The Herald:

But her announcement was greeted with bemusement by Leave campaigners, who said they were not aware that the Muslim peer had ever been a Brexit supporter.

Mr Cameron has faced criticism from some quarters for retweeting a link to the last article written by the Batley & Spen MP, in which she argued that Britain could deal with the issue of immigration more effectively by remaining in the EU.

Mr Farage - who acknowledged on Sunday that Mrs Cox's death had taken momentum out of the Leave campaign - told LBC radio: "I think there are Remain camp supporters out there who are using this to try to give the impression that this isolated horrific incident is somehow linked to arguments that have been made by myself or Michael Gove or anybody else in this campaign, and frankly that is wrong."

He insisted that he had said nothing "inciteful" during the campaign, adding: "What we are seeing here is the Prime Minister and the Remain campaign trying to conflate the actions of one crazed individual with the motives of half of Britain who think we should get back control of our borders and do it sensibly...

"We have a Prime Minister and a Chancellor and other big political leaders in Britain who are scared witless.

"They thought they would win this referendum by a country mile. They know it's neck and neck, they know it's down to who turns out on the day to vote, and there is no level of denigration or false association that they will not stoop to, but I think people are intelligent enough to see through this sort of thing."

Asked during a campaign visit to Cowley, Oxfordshire, whether he was using the MP's death for political advantage, Mr Cameron said: "What I have been talking about in respect of Jo is what a wonderful human being and great politician and great campaigner she was."

He added: "Last week a brilliant Member of Parliament, a loving mother, a loving wife was tragically murdered on our streets.

"What everyone has been saying, and what I say again, is paying tribute not only to her but the values she lived by and epitomised in public life of tolerance, of service, of community.

"That's what we are saying about her."

Lady Warsi condemned as "indefensible" a poster released by Mr Farage hours before Mrs Cox's death, which showed a column of migrants walking through the European countryside under the slogan "Breaking Point".

The Conservative peer told BBC Radio 4's Today programme: "This kind of nudge-nudge, wink-wink xenophobic racist campaign may be politically savvy or politically useful in the short term, but it causes long-term damage to communities.

"The vision that me and other Brexiters who have been involved right from the outset, who had a positive outward-looking vision of what a Brexit vote might mean, unfortunately those voices have now been stifled and what we see is the divisive campaign which has resulted in people like me and others who are deeply Eurosceptic and want to see a reformed relationship feel that they now have to leave Leave."

Mr Cameron said that there were "good ways" of controlling immigration through changes to the welfare system, but added: "A bad thing to do would be to leave the single market, costing jobs, hurting businesses and hurting families' finances right up and down the country.

"That's a risk not worth taking because this is an irreversible decision. Once you have jumped out of the aeroplane door you can't scramble back in again."

Challenged over the poster, Mr Farage said: "If the timing of her murder and me putting out that poster has upset people, I'm sorry. That certainly wasn't the intention. The intention was to use that poster for a day to point out that the EU is a failed project in every sense."

But he described Lady Warsi's defection as "the biggest put-up job I've ever seen", saying she "never supported Britain leaving in the first place" and had refused to appear on campaign platforms.

Senior Leave supporter and Conservative MEP Daniel Hannan questioned whether the Tory peer had been part of the Brexit campaign, saying: "When I invited Sayeeda Warsi to join the Leave campaign, she declined. Fair enough, obviously. But how is this a 'defection'?"

But Lady Warsi said she had spoken for Brexit within the last five weeks and promoted Leave in the media four weeks ago.

"I've been making the case for Leave long before Vote Leave had even formally been established," she said.

Pro-Brexit employment minister Priti Patel dismissed Lady Warsi as "just one voice".

"She is entitled to her view," Ms Patel told reporters during a campaign visit to Maidenhead. "We are seeing a range of voices during this debate. Only at the weekend Lord Guthrie - who famously came out to Remain - has come over to the Vote Leave case for a range of reasons.

"So, she is one voice in this campaign. I think the voices that we need to listen to in this referendum are the voices of the British public, and they will decide the outcome of this referendum on Thursday."

Challenged over whether her defection was a "put-up job", Lady Warsi told Sky News: "People who know me and know my politics know I speak my mind."