With the Brexit vote still on the table, and Theresa May unable to agree a new relationship with the EU, the race for the Conservative Party leadership is expected to be tight.
The party is expected also to make a final decision on whether to make an announcement on the next prime minister by the end of next week.
The race will pit one of the country’s biggest political stars against another – former Tory leader Michael Gove – who has not been endorsed by any other party.
Mr Gove has made a number of key comments in the past week, including calling for an end to UK airstrikes against Syria, and a reduction in immigration.
His comments have drawn criticism from Labour Party leader Jeremy Corbyn, who has been outspoken against Mr Gove’s views on immigration.
But a senior Conservative source told The Independent that Mr Govts comments were “unacceptable” and that Mr Cameron is “willing to be challenged on these matters”.
“The Prime Minister is well aware that he can’t win by telling the truth,” the source said.
“But he’s prepared to challenge the PM on these issues and we are confident he will do so.”
He added that the Tory leader would be a better prime minister if he won the election.
The Conservatives currently hold an 11-seat majority, with Mr Cameron leading Labour in the polls by 11 points.
The result is likely to result in a hung parliament.
The election comes a day after the Conservative party’s leader in the House of Commons, Michael Gidge, was suspended for breaching party rules.
The BBC has reported that Mr Corbyn is “under pressure” to endorse Mr Gidge and to hold a press conference before the election in order to respond to criticism.
He is currently under scrutiny for not having made an endorsement before the June 23 vote, which was postponed due to the government’s decision to delay the vote until August 6.
A Conservative spokesperson told The News: “We have consistently said that we will support Mr Gowts leadership of the Conservative group and are confident that he will stand by that position.”
As we have said from the outset of the leadership contest, we are committed to working constructively with our opponents.
“The Independent has contacted the Conservative leadership for comment.