A study by the National Centre for Social Research for the Financial Times gave Remain a 53-47 point lead, while an ORB poll showed Remain had a 49-47 point lead.
An analysis of the ORB poll for the Telegraph also showed that among definite voters, Remain now has a seven-point lead with 53 per cent of the vote compared to Leave's 46 per cent.
But a YouGov poll for the Times showed that Remain is two points behind Leave on 42 per cent of the vote compared to Leave with 44 per cent.
Polling experts said that the vote's outcome is still too close to call and that the overall picture could change at the last moment.
Mike Smithson, editor of PoliticalBetting.com, wrote in a tweet, "Overall mixed polling results tonight — this is going to the wire."
David Cameron's election strategist, Sir Lynton Crosby, also wrote in the Telegraph that the referendum will "come down to the wire" following the ORB poll.