Insiders have suggested TV judge Rob Rinder or Apprentice-star Karren Brady as possible contenders.
On Tuesday Tory party chairman Greg Hands said the selection process would be “swift, but thorough” with the top candidates taking part in hustings events across London, followed by a vote of London Conservative members.
He said: “[The Mayor’s] Ulez expansion is a shambles that will pile more costs onto hard-pressed motorists living in the outer boroughs and those who travel across the border, to work or visit friends and family.
“He is now facing a high-court challenge.
“We will have a candidate in place by the end of July to give the party 10 months to campaign for change in our capital.”