Theresa May was warned not to call snap general election by campaign guru Lynton Crosby

'There is clearly a lot of risk involved with holding an early election - and there is a real need to nail down the 'why' for doing so now,' memo said

Tory election guru appears to have been against calling a snap election (Getty)

Theresa May was warned by campaign guru Sir Lynton Crosby that her gamble of calling a snap general election carried "a lot of risk", a leaked memo has revealed.

The memo written in April, just days before Ms May announced her surprise decision, said voters did not want the uncertainty an election would cause.

The document, obtained by the Mail on Sunday, warned there was a risk the Tory vote share would end up "broadly similar" to that achieved by David Cameron in 2015 when he won a narrow victory, rather than the landslide sought by Ms May.

When told about the plan to call the June 8 election by Tory campaign chief Lord Gilbert, according to the newspaper Australian Sir Lynton responded by saying: "I'm not sure that's a smart idea, mate."

The leaked "Election Strategic Note - April 2017" memo, drawing on focus group research and national polls, opened by warning that it found "there is clearly a lot of risk involved with holding an early election - and there is a real need to nail down the 'why' for doing so now".

Voters were "actively seeking to avoid uncertainty and maintain the status quo and yet by calling an election the Conservatives are the ones who are creating uncertainty".

It warned that Ms May's strong opinion poll leads at the time meant there were "exceptionally high expectations" she would be returned to Number 10 "leading voters to believe that they can vote for the best local MP while still remaining secure in the knowledge that Jeremy Corbyn will not be PM".

But it also said voters were worried about the risk of a hung Parliament creating "chaos over the delivery of Brexit".

Ms May lost her Commons majority after calling the election and has been forced to rely on a pact with the Democratic Unionist Party to bolster her position in Parliament.

She used a trip to Japan last week to insist that she would stay on as leader and fight the next general election - telling reporters she was "not a quitter" - but opinion polls suggested she should go if the Tories want to remain in office.

A Survation poll for the Mail on Sunday put Labour on 43 per cent, a five-point lead over the Tories on 38 per cent.

Some 42 per cent of voters said it was "unthinkable" that Ms May will fight the next election - including 39 per cent of Tory supporters - and Mr Corbyn was backed by 40 per cent to win the next election, one point ahead of the Prime Minister.

A total of 31 per cent said the Tories were more likely to win the next election if Ms May quit, more than double the 15 per cent who said they were less likely to succeed.

Boris Johnson was backed by 19 per cent to succeed her - 21 per cent among Tory voters - with Jacob Rees-Mogg backed by nine per cent (15 per cent of Tories) and Philip Hammond on eight per cent (12 per cent among Tory voters).

:: Survation interviewed 1,046 people online on Thursday and Friday.

PA