Factbox: UK opinion polls: countdown to Thursday's election

LONDON (Reuters) - With two days to go until Britain holds a national election, opinion polls have shown that Prime Minister Theresa May's lead over the opposition Labour party has ebbed over the last three weeks, with some putting her majority into doubt. Below are details of opinion polls before due before Thursday's vote. SURVATION * A Survation poll showed late on Monday that the lead of May's Conservative Party over Labour stood at just one point. * The poll was conducted on Friday and Saturday, before an attack in London by Islamist militants that killed seven people and injured 48. TUESDAY KANTAR * Likely to be published on Tuesday, 3:30 p.m. (1430 GMT/1030 ET). * The poll is likely to have been conducted after Saturday's London Bridge attack. * A Kantar poll last Wednesday showed May's Conservatives had extended their lead to 10 points over Labour, up from eight in the previous week OPINIUM * Likely to be published on Tuesday evening, London time. * Likely to have been conducted after Saturday's attack. * An Opinium poll for the Observer newspaper on June 3 showed May's lead narrowed to six points compared with 10 a week earlier. WEDNESDAY IPSOS MORI * Ipsos MORI polls for the Evening Standard newspaper have tended to run shortly after 11:00 a.m. London time (1000 GMT/0600 ET). * The last Ipsos MORI published on June 2 showed the Conservatives' lead contracted to five points, compared with 15 points two weeks previously. PANELBASE * Likely to be published on Wednesday afternoon London time, but has sometimes appeared earlier. * A Panelbase poll on Thursday last week showed May's lead almost halved to eight points, compared with 15 points a week earlier. COMRES * Likely to be published on Wednesday evening, London time. * ComRes polls are among those showing the biggest lead for Theresa May. The latest poll, published on Saturday, showed she had a 12-point advantage over Labour, unchanged from a week earlier. ICM/GUARDIAN * Likely to run late afternoon or early evening, London time on Wednesday. * Like ComRes, the ICM polls have shown sizeable leads for the Conservatives, albeit narrowing sharply from record levels around a month ago. * The latest ICM/Guardian poll published on Monday showed May's lead slipped to 11 points, down one point from the previous week. OTHERS YOUGOV * YouGov is likely to publish another poll before Thursday's election but it is not clear when. * Its last poll on June 3 showed May's lead over the Labour party narrowed to four points from seven points a week previously. * A model-based projection from YouGov on Monday showed May was on track to win 305 seats in Britain's parliament in an election on Thursday, 21 seats short of a 326-seat majority. That projection is updated on a daily basis. (Reporting by William Schomberg; Writing by Andy Bruce)