The Conservative Party holds a 22-point lead over Labour, a new poll on Sunday showed.
The ICM figures, reported on by Reuters, showed the Tories at 48 per cent, up two points from last week.
Labour was on 26 per cent, the Liberal Democrats on 10 per cent and Ukip on eight per cent.
The poll emerged after former Prime Minister Tony Blair on Sunday urged voters not to elect MPs who “back Brexit at any cost”, regardless of their political party.
Blair, who said he was “almost motivated” to return to politics because of his passion on the topic of Brexit, described Prime Minister Theresa May’s policy on leaving the European Union as “not reasonable”.
He added: “The point is whether I’m Labour or I’m not Labour – even if there’s Conservatives or Liberal Democrats – I will work with anyone to get this argument across in the country.”
He said he feared a large Tory majority would give May “a blank cheque for Brexit at any costs”.