By Estelle Shirbon and Elizabeth Piper
LONDON (Reuters) - Carmakers and football chiefs threw their weight behind the campaign for Britain to stay in the European Union on Monday, as opinion polls showing the "Remain" camp gaining ground buoyed shares and sterling three days ahead of the referendum.
A senior politician also announced she was defecting to the Remain group, accusing those campaigning to leave the EU of spreading lies, hate and xenophobia.
Britons will cast their votes on Thursday in a referendum that will not only shape the country's role in world trade and affairs but also determine the future of the EU, which has struggled to maintain unity over migration and financial crises.
Both sides restarted campaigning on Sunday after a three-day suspension to honour pro-EU lawmaker Jo Cox who was killed in the street by a man heard shouting: "Britain first. Keep Britain independent. Britain always comes first".
Opinion polls last week suggested the "Out" campaign had made headway in a debate that has polarised Britain. But polling at the weekend - some carried out after the murder - suggested the "In" camp had recovered momentum.
The probability of a British vote to remain in the European Union, implied by Betfair betting odds, rose to 74.6 percent on Monday, up from 60-67 percent on Friday.
Sterling rose 2 percent against the dollar on Monday, putting it on track for its biggest one-day gain for more than seven years, while the FTSE was up more than 2.5 percent. [GBP/] (L)
Prime Minister David Cameron, who is leading the "In" campaign, has focused on the economic argument, telling voters that a Brexit would hurt wages and jobs and lead to a decade of uncertainty.
His cause was bolstered on Monday by senior executives of several carmakers, including Jaguar Land Rover, Toyota, BMW and Vauxhall, releasing statements urging Britons to stay in the EU.
Their trade body, the Society of Motor Manufacturers and Traders, also backed EU membership, saying would be best for business and British jobs.
"We firmly believe Britain would be better off if it remained an active and influential member of the EU, shaping European regulations," said BMW sales chief Ian Robertson.
The head of England's top soccer division - the Premier League - also weighed in, saying that its 20 clubs wanted to stay in the bloc.
"Are we better acting like we want to play our part in the world and be worldly citizens, or do we want to send a signal to the world that says, actually, we're kind of pulling the drawbridge up here?" Richard Scudamore told BBC radio.
JO COX TRIBUTE
The referendum was promised by Cameron in 2013 under pressure from eurosceptic lawmakers from his own ruling Conservative Party, which has been split by the debate along with rest of the country.
After the Cox attack last Thursday, lawmakers called for all sides to tone down the rhetoric in a campaign which has become increasingly heated, often pitting colleagues and friends against each other.
Sayeeda Warsi, a former co-chair of the Conservative Party, said on Monday she was switching her support to the "Remain" campaign because of the tactics used by the other side.
She pointed to a poster from one of the "Leave" campaigns, which used a photo of refugees walking through a field in Europe under the slogan "Breaking Point" - a message she said she did not want to form "the basis of the kind of Britain that I want to live in and to bring my kids up in".
"Are we prepared to tell lies, to spread hate and xenophobia just to win a campaign? For me that's a step too far," she told The Times newspaper.
The "Leave" camp's key argument has been that Britain would be unable to control immigration levels as long as it was in the EU, something that has struck a chord with many Britons who fear that public services are being overstretched.
The leader of the anti-EU UK Independence Party (UKIP), Nigel Farage, whose movement produced the poster, defended it as reflecting the truth. However the official Vote Leave organisation condemned the use of the image - though was dismissive of Warsi's move, saying it did not remember her joining its campaign.
On Monday lawmakers from all the parties were due in parliament to pay tribute to Cox, the first sitting lawmaker to be murdered since 1990.
Several said lawmakers from rival parties should sit alongside each other in the House of Commons on Monday, breaking with decades-long tradition for the ruling party to sit together on one side of the hall, with opposition parties on the other.
"MPs of all parties are united in grief and admiration for Jo," Conservative lawmaker Jason McCartney wrote to the parliamentary speaker, according to local media.
"Would it please be possible and break with tradition and for MPs to mix cross party on the benches on Monday to show we are united in fighting hatred."