Mark Fullbrook is understood to have been promised by Liz Truss that his company would run the Tories’ next general election campaign if he joined her No 10 operation as chief of staff. Sources claimed the “quid pro quo” arrangement, which could be highly lucrative for his lobbying company, Fullbrook Associates, was a precondition of the strategist taking the job. However, it is likely to infuriate Tory MPs with insiders warning of a potential “revolution” on the backbenches as the agreement could mean that Isaac Levido, who ran Boris Johnson’s election campaign in 2019, could be sidelined. It follows the revelation that, in a highly unusual move, the prime minister’s most senior adviser would receive his salary through his company, which may help him minimise tax. In last week’s budget Kwasi Kwarteng, the chancellor, repealed IR35 rules that were introduced in an attempt to stop people paying themselves through companies, rather than being on a payroll, to minimise their tax. Running the Tories’ next election campaign could earn Fullbrook Associates millions, although it was unclear whether his firm had signed a contract with the Conservative party or if the agreement was simply verbal. The Conservatives paid £2.4m to Lynton Crosby’s lobbying firm before David Cameron’s 2015 general election campaign, while his CTF Partners received £4m for advice to Theresa May’s campaign in 2017. Crosby was paid a further £1.6m for his role in Johnson’s 2019 election victory, according to the Electoral Commission, although the campaign was run in-house by his protege, Levido. One government source said of Fullbrook: “There wasn’t a deal as such. But he is chief of staff and [it] wouldn’t be unusual for someone in that position to run the election campaign.” However, senior Conservatives reacted angrily to the move, pointing to Fullbrook’s previous experience of running election campaigns, including Zac Goldsmith’s disastrous bid for London mayor. One Tory insider said: “The prospect of Mark Fullbrook running any election spells electoral doom for the Conservative party. The last time he ran a campaign that faced the UK electorate we got Sadiq Khan [as Labour mayor of London]. With Mark Fullbrook involved the party is destined for opposition.” Another added: “The Tories are abandoning a proven winner for a proven loser. Fullbrook won’t want to do the hard yards. He’ll do six months in No 10 and then hop off to [Conservative Campaign HQ] to plan the election. “You can see the logic. Go in, get settled, move his people into CCHQ and then get a big fat contract to run the election campaign. Win or lose – and it will be a lose – he makes off like a bandit. He’s taking the party for a ride.” Fullbrook’s agreement may mean that Levido, who still works for Tory HQ, could be sidelined at the next election – although some insiders expect him to be asked to stay on in some capacity. Another Tory source described it as a “quid pro quo” arrangement, but pointed out that the Tory party may be tied into a contract with Levido’s company, Fleetwood Strategy. They added: “There would be a revolution on the backbenches. Isaac is considered to have run a brilliant campaign in 2019. Fullbrook’s previous electoral experience was running Zac Goldsmith’s disastrous campaign for London mayor.” Fullbrook had previously told the Guardian that he had stopped all commercial activities of his lobbying company as of 31 August this year. The firm was only set up earlier this year and has previously counted as clients Libya’s “parliament”, which has twice attempted to overthrow the UN-established government of national unity in Tripoli, and Sante Global, formerly Unispace Health, which was awarded a £680m PPE contract in 2020. Kwarteng said he had no knowledge of the employment arrangements, but praised Fullbrook for enhancing the government. A spokesperson for Fullbrook said: “This is not an unusual arrangement. It was not put in place for tax purposes and Mr Fullbrook derives no tax benefit from it.” But Labour’s deputy leader, Angela Rayner, said: “The shocking revelation that the prime minister’s chief of staff is on loan from a lobbying company, not actually employed by the government, raises serious questions about the new prime minister’s judgment. “The fact that this bombshell comes days after alarming reports that Mr Fullbrook is also embroiled in a foreign bribery probe involving the FBI will only add to public concern. “While Liz Truss shows all the signs of allowing another wave of Tory sleaze to fester, a Labour government would create an independent ethics and integrity commission to clean up public life and restore the basic standards we expect.” A Cabinet Office spokesperson said the arrangement had been cleared by the government’s propriety and ethics team. “All government employees are subject to the necessary checks and vetting, and all special advisers declare their interests in line with Cabinet Office guidance. It is not unusual for a special adviser or civil servant to join government on secondment. Any government employee hired on secondment is subject to the usual special adviser or civil service codes.” They added: “The government will pay the salary of an employee on secondment, including costs such as employers’ national insurance contributions, to the seconding company. This has been cleared by the propriety and ethics team in Cabinet Office.” Fullbrook is already facing questions over his role in government after it emerged he was questioned as a witness as part of an FBI inquiry into alleged bribery in Puerto Rico. At the time, Truss’s spokesperson said she was backing Fullbrook, who did not travel with her to the UN general assembly in New York last week. The prime minister herself declined to say whether she had been told about his cooperation with the FBI before his appointment, saying only that it had gone through the “proper process”. A Downing Street spokesperson said the prime minister stood behind Fullbrook 100% and he had “her full support”.