The chair of the committee of Conservative backbenchers has suggested the former prime minister Boris Johnson had the backing of enough MPs to mount a challenge to Rishi Sunak in last month’s leadership contest. Johnson dropped out of the race, claiming he had the nominations needed to make it on to the ballot paper but could not unite the party. His supporters’ claims that he had reached the threshold of nominations to secure a place on the final ballot were met with scepticism by politicians across the divide as well as commentators. However, speaking to the BBC, Sir Graham Brady, the chair of the Conservative party’s 1922 Committee, said two candidates had reached the threshold, and “one of them decided not to then submit his nomination”. Brady spoke about his experiences meeting Liz Truss and Johnson at separate stages this year to tell them they no longer commanded majority support from their MPs. He told BBC North West Tonight that Truss had “come to the same conclusion” as him regarding the untenable status of her premiership, while Johnson was “still determined to go on” the night before he announced his resignation. After Sunak was made prime minister uncontested, Johnson tweeted: “Congratulations to Rishi Sunak on this historic day, this is the moment for every Conservative to give our new PM their full and wholehearted support.” The former prime minister offered his congratulations a day after messages from the outgoing PM Truss and Sunak’s fellow leadership hopeful, Penny Mordaunt. In his speech, Sunak said he would “always be grateful” to Johnson for his “incredible achievements” in No 10. He pledged to deliver on the Conservative 2019 manifesto. He said: “I will always be grateful to Boris Johnson for his incredible achievements as prime minister and I treasure his warmth and generosity of spirit. “I know he would agree that the mandate my party earned in 2019 is not the sole property of any one individual, it is a mandate that belongs to and unites all of us. And the heart of that mandate is our manifesto. I will deliver on its promise.” In a statement, Johnson said there was a “very good chance” he could have been back in No 10 by the end of the week if he had stood. However, his efforts to “reach out” to his rivals – Sunak and Mordaunt – to work together in the national interest had not been successful so he had decided to drop out.