Sir John Major has hit out at the use of "puerile" political slogans as he called for more honesty in government about the challenges facing the UK.
The ex-prime minister said political leaders should avoid "deceitful" sound bites and be more candid about the limitations of what government can do.
In a speech in London, he recounted how his use of the phrase "back to basics" in 1993 had ended up "perverting a thoroughly worthwhile social policy".
Sir John was PM between 1990 and 1997.
Addressing an audience in Westminster Abbey, Sir John also warned about factionalism in his party and the British political system as a whole and of the risk that "partisan" voices "appealing to the extremes" posed to democracy.
"The anti-European right wish to control the Conservative Party," he said. "The neo-Marxist left wish to dominate Labour. Both are making headway in a battle for the soul of their respective parties."
In a strong attack on what he suggested was the debasing of modern politics, he called for special advisers to be reined in, saying they were being used as "attack dogs", leaking material and usurping civil servants.
He suggested the language of politics was being corrupted by the tendency of politicians to fall back on pre-prepared and meaningless sound bites.
Sir John, who has called Brexit a historic blunder, cited the Leave campaign's promise during the EU referendum to "take back control" as a "memorable example of pitch-perfect absurdity".
Such slogans, he argued, "convey nothing, explain nothing and are worth nothing".
"As voters hear our elected representatives uttering puerile slogans instead of explaining policy, it is no wonder if respect for them melts away. Slogans and sound bites are a deceit.
"Electors deserve the truth in plain English, not in fairy tales."
Sir John conceded his own use of the phrase "back to basics" in his 1993 Tory conference speech - in which he called for more emphasis on personal responsibility, respect for law and order and a return to "the old values of neighbourliness, decency and courtesy" - was counter-productive.
Because it was followed by a string of sex and financial scandals involving ministers, the speech came to be associated with personal morality and probity.
"They [slogans] can mislead," he added. "I once used the phrase back to basics and it was taken up to pervert a thoroughly worthwhile social policy."
Theresa May was criticised for her frequent use of the phrase "strong and stable" during the election campaign while Jeremy Corbyn relied heavily on his claim to be "for the many not the few".
In his speech, Sir John warned that the massive task of extricating the UK from the EU was "crowding" out other vital issues and said his party needed to talk more about levels of income disparity and regional imbalances which "surely cannot be permitted to continue as they are".