Boris Johnson's key ally in the Conservative leadership contest, justice secretary Michael Gove, had concerns about his candidacy, according to an email from Mr Gove's wife, Sarah Vine.
In the email, which was accidentally sent to a member of the public and passed on to Sky News, Ms Vine urges Mr Gove to work on overcoming “individual obstacles” before endorsing Mr Johnson.
“You MUST have SPECIFIC assurances from Boris OTHERWISE you cannot guarantee your support. The details can be worked out later on, but without that you have no leverage,” the email said.
Mr Johnson, who is taking advice from election guru Lynton Crosby, remains the favourite to succeed David Cameron.
But some Conservative MPs have expressed doubts about the former London mayor and leading Leave campaigner's suitability and backbencher Alan Duncan yesterday jokingly compared him to former Italian prime minister Silvio Berlusconi.
Sir Alan asked Mr Cameron "how in terms of their countries' reputation and success he would compare the undemonstrative competence and dignity of Angela Merkel with the theatrical and comical antics of Silvio Borisconi".
Formal declarations
Nominations for the leadership opened yesterday evening, with work and pensions secretary
Stephen Crabb
becoming the first candidate to formally declare.
Mr Johnson and home secretary Theresa May are expected to announce their candidacies shortly before nominations close at noon today, with other potential candidates still considering their options.
Mr Crabb, who is running on a joint ticket with business secretary Sajid Javid, who would become his chancellor, stressed his background growing up on a council estate as the son of a single mother.
"She took us to the public library every Saturday where I soaked up books and learning; I worked every week from the age of 12 – starting at the local corner shop, graduating to the Tesco shop floor, and paid my way through university working on building sites in various parts of the country," he said.
“Now I count myself very blessed to have had the upbringing I did. I was brought up to believe no one was better than me and I was no better than anyone else.”
A devout Christian who opposed same-sex marriage, Mr Crabb took a swipe at Mr Johnson, who once said he would go for the premiership if the ball came loose from the back of the scrum.
"I was brought up to understand that nothing gets handed to you on a plate. On the rainy rugby fields of west Wales I learned that it's not a question of just waiting for the ball to pop out from the back of the scrum. If you want it, you do what's required," Mr Crabb said.
