Mr Greenhalgh, who heads the Mayor’s Office for Policing and Crime, is currently the most senior Tory politician to declare an interest in standing in the 2016 Mayoral elections.
He has promised to slash fares by 3% a year, reversing Mr Johnson’s seven years of above inflation increases.
Greenhalgh’s promise contradicts the Mayor’s repeated insistence that cutting fares, as called for by opponents on the London Assembly, would mean slashing investment in London’s transport network.
During the 2012 Mayoral race Johnson poured scorn on claims by rival Ken Livingstone that a fares cut was affordable and has increased fares each year since his re-election.
Val Shawcross, Labour’s Transport spokesperson on the Assembly, said Mr Greenhalgh’s promise shows the Mayor has “lost control” of his team.
She added: “What we see here is the wheels totally coming off Boris’ mayoralty. With even his own Deputy openly criticising his fares policy it’s never been clearer that Boris has completely lost control.
“This is an incredibly cynical announcement from Stephen Greenhalgh, given that for seven years he has been silent on Boris’ fares hikes and has helped to prop up a Mayor who has raised Londoners’ travel fares by over 40%.”
Mr Greenhalgh’s fares vow is the second time he’s contradicted his boss in recent weeks.
Last month he told the London Assembly that the Mayor and former policing Deputy Kit Malthouse had failed to prepare the Met for impending budget cuts.
The Mayor later described the comments as “nonsense”.
Commenting on the fares row, Boris Johnson today said: “I’m very proud of what we’ve been able to do in London to keep fares at RPI over the last 2 years.
“We are going to continue to bear down on fares, as I promised in 2012, but only in so far as is consistent with the vital investment we need to meet the increasing demand posed by London’s growing population whilst still providing a fantastic service for all passengers in London.
“As for future mayoral hopefuls or candidates they have to take their decisions, but mine are based on what is best for the city.”
