LONDON (REUTERS) - Opinion polls published in the days before Thursday's (June 23) referendum have mostly shown a shift towards keeping Britain in the European Union, but the "In" camp's lead is small and most pollsters say the race still looks too close to call.

Prior to this week's polls, in the period between June 10 and June 16, "Out" led in seven of nine polls, rattling investors in markets around the world.

Betting odds, provided by gambling firm Betfair, gave the "Remain" campaign an 80 per cent probability of winning, up from as low as 59 per cent last week.

Here is a summary of the most recent polls:

COMRES/ITVITV/DAILY MAIL - "REMAIN" AHEAD BY 6 POINTS

A ComRes telephone poll of 1,032 adults showed "Remain" on 48 per cent and "Leave" on 42 per cent on Wednesday, compared with a 46 per cent-45 per cent split in a previous poll on June 14.

Excluding those who didn't know how or if they would vote, "Remain" was on 54 per cent and "Leave" on 46 per cent.

YOUGOV/THE TIMES - "REMAIN" AHEAD BY 2 POINTS

A YouGov online poll of 3,766 adults showed "Remain" on 51 per cent and "Leave" on 49 per cent, after weighting responses for likely turnout and excluding those who did not know how they were likely to vote.

A previous YouGov poll for the Times on June 20, which used different adjustments, showed "Remain" on 42 per cent and "Leave" on 44 per cent."

TNS - "LEAVE" AHEAD BY 2 POINTS

The campaign for Britain to leave the European Union has a two-point lead over the rival "In" camp, down from a seven-point lead last week, according to a TNS poll published on Wednesday. TNS said 43 per cent of respondents would vote to leave, while 41 per cent would vote to remain and 16 per cent were undecided or did not intend to vote.

OPINIUM - "LEAVE" AHEAD BY 1 POINT

Opinium said the campaigns were effectively running neck and neck as the online poll put support for "Leave" at 45 per cent and "Remain" at 44 per cent, with the remaining 9 per cent of respondents still undecided.

The poll was based on 3,011 interviews conducted between June 20 and 22.

Opinium's previous poll, published on Saturday, had put the two camps level at 44 per cent, based on polling between June 14 and 17.

SURVATION/IG - "IN" AHEAD BY 1 POINT

A Survation poll of just over 1,000 people for IG Group on Tuesday put the "In" camp at 45 per cent, ahead of "Out" on 44 per cent, representing a narrowing of its lead.

Survation's previous poll, for the Mail on Sunday newspaper and published late on Saturday, had shown "In" ahead of "Out" by 3 percentage points.

The new Survation poll was conducted by telephone on Monday. Excluding the 11 per cent of respondents who answered "don't know", the survey gave "In" a lead of 51-49 per cent, IG said.

ORB/DAILY TELEGRAPH - "IN" AHEAD BY 7 POINTS

An ORB telephone poll of 800 people for the Daily Telegraph newspaper, published late on Monday, put support for "In" at 53 per cent, with "Out" on 46 per cent.

The previous poll by ORB, published a week earlier, had put the "Out" camp ahead by one point.

"All the signs of ORB's latest and final poll point to a referendum that will truly come down to the wire," said Lynton Crosby, a political strategist who advised the ruling Conservative Party at the last national election in 2015.

YOUGOV/THE TIMES - "OUT" AHEAD BY 2 POINTS

A YouGov online poll for the Times newspaper, also published late on Monday, gave "Out" a 44-42 per cent lead over "In."

YouGov's previous poll had put "In" one point ahead when it was published in the Sunday Times newspaper.

The survey interviewed 1,652 people between Friday and Sunday. Of those questioned, 9 per cent said they did not know how they would vote and 4 per cent said they would not vote.

NATCEN - "IN" AHEAD BY 6 POINTS

A poll from the social research organisation conducted between May 16 and June 12 put the "In" camp on 53 per cent, while the "Out" camp was on 47 per cent.

The survey, conducted online and by telephone, had a sample size of 1,632 respondents. Sixty-five per cent of the interviews were done by May 26.

TELEPHONE POLL BY IPSOS MORI

Details of a telephone poll by Ipsos MORI for the London Evening Standard newspaper are expected to be published on the morning of the referendum. The findings of a YouGov poll, based on interviews conducted online on Thursday, are due to be announced by Sky News after the close of voting at 2100 GMT.