Briefing document made after Liberal Democrat leader's rehearsals for debate reveal he was urged to 'look more relaxed'

This article is more than 10 years old

This article is more than 10 years old

The secrets behind Nick Clegg's performance in last week's televised leaders' debate have been revealed after a Liberal Democrat aide left briefing notes for the head-to-head appearance in the back of a black cab.

Most polls showed the Lib Dem leader to have been a clear winner of Thursday's debate, transforming the political picture in the UK.

His performance has seen the Lib Dems surge in popularity, with some polls putting the party – used to being in third place – above both Labour and the Conservatives.

The odds on Clegg becoming prime minister have plummeted from 300-1 before the debate to 12-1.

The dossier – entitled "I'm not here right now" and written by John Sharkey, the chairman of the Lib Dem election campaign team – was handed to the Sun.

It reveals Clegg had not been as effective in rehearsals as he was in front of the cameras.

Sharkey told him to show "more passion/conviction" and to "speak more slowly", and warned that he was being "too repetitive". The Lib Dem leader was urged to "look more relaxed" and use "shorter, simpler answers".

He was also taken to task for being "offensive" when he talked about assisted suicide in terms of a pet being put down.

The dossier reveals differences in the Lib Dems' perception of Clegg's political rivals. While it urged him to take a leaf out of David Cameron's book, Gordon Brown's use of language was described as "weird".

"DC [David Cameron] talks a lot in the language of values. We need to do this," the document read. It told Clegg to attack the prime minister for "weird language, no real promises and lots of fudge".

Clegg, who successfully put ideological distance between his party and Labour and the Tories during the debate – at one point, he said of his opponents: "The more they attack each other, the more they seem exactly the same" – was told in the notes to "constantly stand back" from his rivals.

The document highlighted Lib Dem concerns that their policy to scrap government plans to renew Trident would come under attack, with "avoid unilateral disarmament implication" written out in block capitals.

Although the party wants to scrap Trident, it insists it will retain a nuclear deterrent that can be negotiated away with other nuclear-armed countries.

Clegg reacted in a lighthearted manner to the discovery of the dossier, telling a press conference this morning: "I'm glad to see my top team is preparing for government by developing the habit of leaving secret dossiers in the back of cabs.

"I have always been advised just to be myself in the debates. That's exactly what I was, and that's what I will continue to do."