Boris Johnson’s former adviser on ministerial standards was prevented from interviewing a key witness for his bullying inquiry into Priti Patel’s behaviour. Legal and Whitehall sources have revealed that Sir Alex Allan sought to interview the former top Home Office civil servant Sir Philip Rutnam about his dealings with Patel, but was blocked by government officials. The inquiry was launched by the prime minister following the resignation of Rutnam over Patel’s alleged behaviour. Rutman is suing the government for constructive dismissal. Sources say Allan was informed he could not interview Rutnam because of the legal action. Allan, however, felt that his inquiry was being denied potentially crucial evidence. Even so, he uncovered sufficient material about her behaviour in three separate departments to conclude Patel had broken the code governing ministers’ behaviour. A Cabinet Office spokesman said on Saturday: “Alex Allan was satisfied he had all the information that he needed to reach his findings.” On Friday Allan resigned after the prime minister took the unprecedented step of rallying his MPs behind an effort to defend Patel, who has refused to resign. Offering what she described as an “unreserved, fulsome apology”, Patel seized on Allan’s finding that she had received no feedback on the impact of her behaviour. This is challenged by Rutnam, who said she was clearly advised not to shout and swear at staff the month after her appointment in 2019 and that he told her to treat staff with respect “on further occasions”. The latest revelation undermines one of the main mitigating factors in Allan’s report – that “no feedback was given”. Had Rutnam been interviewed, it appears unlikely it could have concluded she had not been made aware. The revelation fuels the growing concern over the prime minister’s handling of the controversy. Sir David Normington, a former Home Office permanent secretary, said on Saturday that Boris Johnson “doesn’t seem willing to stand up for high standards in public life”. The prime minister had “simply put aside the findings of a report, and of the independent adviser Sir Alex Allan, that she is a bully, and you shouldn’t have bullies in government”, Normington told BBC Radio. “We have to put ourselves in the position of the bullied. No one has spoken up for them. Some of them are junior staff who will be sitting there today thinking that their voice has not been heard and you cannot rely on the prime minister to stand up for them.” The Conservative peer Ken Clarke, a former home secretary, said he was “troubled” by the “very awkward situation”. “It was assumed before that if an investigation was taken this far and if anyone was found to have broken the ministerial code, I don’t think anyone would have doubted the minister – to use the old phrase – would have to consider his or her position,” Clarke told Times Radio. Meanwhile, a former Tory cabinet minister said the fact that Patel could survive was extraordinary enough, but equally incredible was the prime minister’s behaviour in rallying his MPs behind an effort to defend her. The senior figure, now on the backbenches, said: “He [Johnson] has a formal role, a kind of judicial role. He should at least try to show respect for that. Instead he just sticks two fingers up at the whole process.” On Saturday questions emerged about whether Johnson attempted to tone down the bullying report, amid claims Allan had resisted pressure to make the findings more “palatable”. Downing Street did not deny the claim, with a No 10 spokesman saying: “As you would expect, the prime minister spoke to Sir Alex Allan to further his understanding of the report.” Sources with knowledge of Allan’s inquiry into Patel confirmed he had come under “a lot of pressure”. “Allan bent over backwards to be as fair as possible to the home secretary but the weight of evidence was such that he still came to the conclusion that Patel had bullied staff,” said a legal source. It has also emerged that Allan’s investigation was conducted far more quickly than previously reported and was on the prime minister’s desk as early as April. It means Johnson elected to sit on its damning findings for seven months until pressure grew so intense he had no option but to make its findings public. Away from Westminster, senior figures from the immigration and asylum sector said Patel’s refusal to resign had destroyed any shred of political legitimacy she had. Bella Sankey of Detention Action said: “Given her conduct since becoming home secretary, she’s become a byword for a joke.”