THERESA May has warned her senior colleagues to guard against complacency, telling them not to think that, because the Conservatives have a commanding lead in the opinion polls, this means the June 8 General Election is in the bag.

Recent snapshots have given the Tories a 21 per cent lead; one at the weekend placed them on 50 per cent of the vote, giving them a 25-point lead over Labour.

The Prime Minister used a political meeting of the Cabinet in Downing Street to remind ministers that polls had been proved wrong "repeatedly" in the EU referendum, the 2015 General Election and the US presidential election.

Echoing comments made by the Labour leader himself, Mrs May pointed out that bookmakers were initially offering odds of 200-1 against Jeremy Corbyn taking the helm of his party in the race to succeed Ed Miliband.

And party chairman Sir Patrick McLoughlin said it would be necessary for Tories to "campaign hard for every vote, in every part of the country".

Senior Conservatives have repeatedly talked up the prospects of Labour doing well, in what is seen by many Westminster observers as an effort to avoid complacency among its supporters.

There are fears among Tory strategists that if their supporters believe victory is a foregone conclusion, they might not turn out at the polling stations in six weeks’ time.

Mrs May’s visit to Wales coincided with a dramatic opinion poll, which suggested her party would become the largest there, gaining 10 seats to take 21.

She told her ministers at the No 10 meeting that it was important to get across the message that the country was being offered a choice between what she termed "strong and stable leadership" under her or "a coalition of chaos and instability led by a floundering, weak and nonsensical Jeremy Corbyn that will put our nation's future at risk".

Later on the stump in Wales, she described the forthcoming election as the “most important” one of her lifetime.

Making clear she would be fighting a "positive campaign," she told activists in Bridgend: "It is only you the people who can give us the mandate. Give me a mandate to fight for Britain and give me a mandate to deliver for Britain."

On Brexit, the PM noted: "In terms of the single market…we want the best possible deal for trading with the European Union. We want the best possible tariff arrangements…to ensure that that trade can continue. We are not talking about access to the single market we are talking about trading with the single market."