BARONESS Warsi, a former Conservative chairman, has switched her support from Leave to Remain in the EU referendum debate, complaining that moderate voices in the Brexit campaign have been drowned out by "lies and xenophobic campaigning".

The Tory peer said her decision to change sides was sparked by an "indefensible" poster released by Ukip leader Nigel Farage, as well as "lies" from Michael Gove, the Justice Secretary, over the prospect of Turkey joining the EU.

But her defection was greeted with bemusement by the Leave campaign with senior figures saying they were not aware that she had been a supporter.

Mr Farage said on Twitter: "Baroness Warsi 'defection' is a typical Number 10 put-up job. She never wanted to leave the EU."

The development came as MPs gathered in Westminster for a recall of the UK Parliament to pay their respects to Labour MP Jo Cox, whose death in a violent attack on Thursday led to a three-day pause in the EU battle.

Campaigning was expected to get back into full swing, with both sides making a final push for support in what appears to be a knife-edge vote.

HeraldScotland:

Leading Leave campaigner Boris Johnson issued an appeal for voters to "change history" in the June 23 vote.

Writing in the Daily Telegraph, the former London mayor said the country was facing a "moment of fundamental decision" with a chance to transform Britain's democratic arrangements for the better.

"Now is the time to believe in ourselves, and in what Britain can do, and to remember that we always do best when we believe in ourselves," he said. "This chance will not come again in our lifetimes, and I pray we do not miss it.

"You can change the whole course of European history - and if you vote Leave, I believe that change will be overwhelmingly positive."

Lady Warsi - who was the first Muslim woman to attend Cabinet but quit the Government in 2014 over the Gaza conflict, announced her defection in The Times, saying she could not support a campaign which included the Ukip "Breaking Point" poster depicting a column of migrants walking through the European countryside.

She later told the BBC Radio 4 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."

Lady Warsi said she had argued for a "Hello World" approach to the Leave campaign, stressing "an optimistic vision of where Britain stands in the world, how it trades freely and is open to the brightest and best from around the world and is rooted in its humanitarian instinct".

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'?"

And prominent Brexiteer Toby Young asked: "Was Warsi on our side? Who knew?"

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, campaigning for Brexit last summer, building the foundation of bringing on different communities to make sure that their voice too would be heard in this Brexit campaign," she said.

Lady Warsi's announcement came the morning after David Cameron's final TV setpiece of the referendum campaign, as he faced an often hostile grilling from members of the public on BBC1's Question Time in Milton Keynes.

The Prime Minister was clearly stung by one man in the audience who likened him to a "21st century Neville Chamberlain waving a piece of paper in the air saying to the public 'I have this promise'" - a reference to the appeasement of Hitler in the 1930s.

He rejected the comparison of the EU to a "dictatorship" and invoked the wartime spirit of Winston Churchill to urge voters to carry on the fight for British values within Europe.

"I don't think Britain at the end is a quitter. I think we stay and fight. That is what we should do. That is what made our country great and that's how it will be great in the future," he said.

Also appearing on Today, Mr Farage defended his poster, saying: "I didn't invent that picture. The picture was real, the picture was on the front pages of all our national press last year.

"We planned to run six posters in the last week of the campaign. This poster was designed for the day. It was unfortunate timing that, within a couple of hours of releasing it, this terrible tragic murder took place and, when we saw that, we immediately withdrew the poster because we understood that it was a day for everybody to go quiet and be silent."

Mr Farage said he accepted that the economic argument on whether the UK should be in the EU may be finely balanced, but there were other issues which made Leave the right choice.

"I would accept that economically, it is about even-Steven, but I do think there is an issue here called the quality of life," he said. "If you can't get a GP appointment or your kids can't get a house or you can't get your five-year-old into a local primary school, those are real issues."

The UKIP leader said Britain currently had a "rotten deal" with the EU and should offer after Brexit simply to continue trading with the remaining Union on a tariff-free basis.

Asked what he would do if this offer was rejected, he said: "If they cut off their noses to spite their faces, then 'no deal' is better than the deal we currently have."

On what would happen if Britain voted Remain on Thursday, Mr Farage said: "If this proposition gets rejected, then we will not be the first country to leave the EU - the Danes or Swedes or Dutch will beat us to it. Believe me, this project is doomed.

"But I still think we are going to win because those who want to leave have made their minds up and believe in it," he added.

Meantime, the Leave-supporting former director-general of the British Chambers of Commerce, John Longworth, told Today that Britain could boost its GDP growth by 1.1% simply by ending contributions to EU budgets and saving 10% of the cost of European regulation.

"The single market isn't a nirvana, it's a mirage," said Mr Longworth. "The single market is a protectionist area. We would be able to remove external barriers, reduce the cost of clothing and footwear, reduce the cost of food products we can't produce in the UK, because at the moment the EU puts up tariffs for the rest of the world, which we have to pay for."

He said a growing number of businesses were backing Brexit, adding: "The cost of membership of the single market club outweighs massively any benefits the single market provides ... We are shackling ourselves to a dead carcass; we need to get out there and embrace the world."