THERESA May has warned her senior colleagues to guard against complacency as she took the campaign fight to Labour’s Welsh heartlands, branding Jeremy Corbyn “floundering, weak and nonsensical”.

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 Mr Corbyn taking the helm of his party in the race to succeed Ed Miliband.

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

Recent UKwide opinion polls have given the Conservatives a significant 21-point lead over Labour; one at the weekend put the Tories on 50 per cent with a 25-point lead.

Indeed, this week a snapshot in Wales placed the Tories on 40 per cent of the vote, suggesting that they could be looking at gaining 10 seats, taking their total to 21; the first time in modern times that they would have been the largest party in Wales. Such a result would see Mrs May’s party taking seats like Wrexham, Newport East, Cardiff West and Bridgend.

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.

At the No 10 meeting, the PM told her ministers 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".

On the stump in Bridgend, Mrs May described the forthcoming election as the “most important” one of her lifetime.

Making clear she would be fighting a "positive campaign," she told activists: “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."

She went on: "A vote for any other party would be a vote for a weak and failing Jeremy Corbyn propped up by a coalition of chaos which would risk our national future."

Asked about the claims Tory high command was considering a tax “sweetener” for working people, which could help in such Labour heartland seats as Bridgend, Mrs May said: "There's a choice between a Conservative Party which always has been, is and will always be a party that believes in lower taxes…and a Labour Party whose natural instinct is always to put up taxes."

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."

Alun Cairns, the Welsh Secretary, added that it was an “extremely important time for the Union of the UK,” noting: “It's never been more relevant than it has for generations because the Union of the UK will deliver that economic prosperity and that stability that we have seen start to recover over recent years."