The latest Brexit poll is showing a 6-point swing back to the Remain campaign

The campaign for Britain to stay in the European Union has taken a three-point lead over the rival "Out" camp ahead of Thursday's EU membership referendum, according to the first opinion poll conducted after a fatal attack on a lawmaker.

The Survation poll for the Mail on Sunday newspaper put support for "In" at 45% ahead of "Out" on 42%.

The Mail On Sunday endorsed the campaign to remain in the European Union, its deputy news editor said on Saturday.

Survation's previous poll, which was conducted for financial markets firm IG, had shown "Out" ahead of "In" by 45% to 42%.

That poll was published on Thursday shortly before Jo Cox, a member of parliament for the opposition Labour party, was shot and stabbed to death by a man who gave his name as "death to traitors, freedom for Britain" when he appeared in court on Saturday.

The new Survation poll was conducted on Friday and Saturday.

This swing is the latest in an unpredictable campaign. The Leave campaign, which had been trailing Remain for months, had taken the lead in the polls last week.

On Monday, three polls published within the space of just four hours all indicated leads for Leave. Surveys produced by Survation, Ipsos MORI, and BMG had all given leads to Leave.

Here's the chart from Macquarie: