Both campaigns hit pause for three days following the fatal shooting of Labour MP Jo Cox, a pro-EU campaigner.
Rival camps vied to seize momentum Monday for the final stretch before Britain's referendum on the European Union membership, after the shock killing of a lawmaker halted the campaign.
Politicians will return to parliament, which had been in recess, for a special sitting to pay tribute to Jo Cox, a pro-EU campaigner murdered on a village street last week.
Politicians on both sides of the debate sought to lay out their case to voters with just three days left until the ballot.
"You can change the whole course of European history," wrote pro-Brexit campaigner and former mayor of London Boris Johnson in the Daily Telegraph.
"I hope you will vote Leave, and take back control of this great country's destiny," he implored. "This chance will not come again in our lifetimes, and I pray we do not miss it."
Prime Minister David Cameron called on voters to pick "Remain" in a heated BBC television appearance on Sunday evening in which an audience member accused him of appeasing an EU "dictatorship".
"If we do leave, we are walking out the door, we are quitting," Cameron urged.
"I don't think Britain at the end is a quitter. I think we stay and fight. That is what we should do."
The Leave and Remain sides have battled each other to a stalemate with each have exactly 50 percent support, according to an average of polls calculated by research site What UK Thinks.
The vote on Thursday could see Britain become the first country to leave the 28-member European Union, a prospect that rattled markets last week, when the Leave side appeared to be gaining.
Opposition Labour leader, Jeremy Corbyn, is due to be grilled by a live television audience later on Monday as he makes his case for Remain.
The murder of fellow Labour party politician Cox, who was known for her pro-EU stance and refugee advocacy, caused widespread shock and raised questions on whether the tone of the campaign had been divisive.
Her alleged killer, Thomas Mair, replied "Death to traitors, freedom for Britain" when asked to give his name at a court appearance on Saturday.
Criticism has focused on a poster unveiled by the Leave campaign showing a queue of migrants and refugees on the border of Slovenia, with the words "Breaking point" in large red letters.
Finance minister George Osborne called it "disgusting and vile" and said it had "echoes of literature used in the 1930s".
Another senior Conservative politician, Sayeeda Warsi, announced she was withdrawing support for Leave due to the poster.
"That 'breaking point' poster really was—for me—the breaking point to say, 'I can't go on supporting this'," Warsi told The Times.
"Are we prepared to tell lies, to spread hate and xenophobia just to win a campaign?"
Some leave campaigners said they were unaware that Warsi was part of their campaign.
Been part of the leave campaign from start. I had no idea that @SayeedaWarsi was part of the leave campaign. News to all of us me thinks.— Nadhim Zahawi (@nadhimzahawi) June 19, 2016
However, a tweet she wrote in early June shows her support for Brexit.
For those of us committed to @vote_leave this unholy alliance between small minded little islanders & optimistic hello worlders is a strain!— Sayeeda Warsi (@SayeedaWarsi) June 7, 2016
The Leave side has in turn accused Remain of scaremongering with its warnings of recession if Britain leaves the EU.
Farage has dismissed criticism of the poster and denied stirring hatred, but conceded Sunday that the murder of Cox may have tempered the upward march of his campaign.
"We did have momentum until this terrible tragedy," he told ITV. "When you are taking on the establishment, you need to have momentum."