Writing in the Daily Telegraph, Mr Hague who led the party from 1997 to 2001, said that candidates need to be ready for what will hit “hit them”. His warning came ahead of today’s hustings, the first official one for the leadership campaigns. The former Foreign Secretary said: “It is by no means clear as things stand that all of the leading candidates have that plan in their head, and are ready for what is going to hit them if they win the leadership.
“The risk is that they will make tactical decisions and statements in the opening hours that will progressively enfeeble them over the subsequent weeks.”
Mr Hague said his “hero” William Pitt the Younger taught clear lessons after spending 17 years as Prime Minister after being appointed by the King following the collapse of the Fox-North coalition in 1783.
The intervention is likely to be seen as a dig at Boris Johnson who has criticised for his lack of detailed planning.
Candidate Rory Stewart criticised his adversaries for making spending pledges they would be unable to keep in office.
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Describing some of the promises as “eye-watering”, Mr Stewart said they would undermine the party’s reputation for economic success.
Mr Stewart said the pledges of Mr Johnson, Michael Gove, Jeremy Hunt, Sajid Javid and Dominic Raab would cost £84billion.
The International Development Secretary said: “We simply cannot make spending and tax cut promises that we can’t keep.
“We cannot criticise Jeremy Corbyn for reckless spending pledges if we start doing the same ourselves. Cheap electoral bribes could cost us dear.”
According to Mr Stewart’s team, Mr Raab was the worst offender with proposed cuts of £38.2billion.
They include raising the national insurance threshold to £12,500, scrapping stamp duty on homes under £500,000, and a 5p cut in the basic rate of income tax.
Mr Gove’s promises to scrap VAT and replace it with lower and simpler tax would cost £20billion, as reported by PA.
Mr Hague’s successor as Tory leader Iain Duncan Smith did back Mr Johnson, however.
Mr Duncan Smith said: “Boris is, as he showed in London, capable of also capturing a mood of optimism for too long missing in our message to the electorate.”
Andrea Leadsom is expected to vow to tackle climate change at her launch today.
She is set to present herself as “optimistic yet realistic Brexiteer”.
She is expected to back moves to a carbon neutral economy, and back a major expansion to housebuilding, putting young people on the ladder and supporting those who wish to downsize.
“Our party has thrived in the past when it has governed as a champion of the people, providing freedom of choice and opportunity, a strong economy and global leadership,” she is expected to say.
Matt Hancock, Mark Harper and Esther McVey are the other candidates in the running.
Thursday will see the ballot amongst Tory MPs with MPs requiring 5 percent or 16 votes to remain in the running.
Subsequent ballots will be held on June 18, 19 and 20 with candidates then requiring 32 votes or 10 percent to stay in contention.
This continues until just two MPs remain.
Then a ballot of the more than 160,000 party members will be conducted with the winner expected to be announced on the week beginning July 22.
Until this point, Theresa May will remain as Prime Minister and acting party leader.
