Sadiq Khan’s record has been criticised after it emerged that only 35 parents had taken up a childcare deposit scheme out of more than 75,000 employees.
The mayor launched the interest-free loan at the start of 2017 and called on London businesses to follow his lead.
He promised to help his employees with the high costs of childcare by providing upfront fees.
But two-and-a-half years later just 35 employees working in organisations run by Mr Khan have benefited from his loan.
Lib Dem London Assembly Member Caroline Pidgeon, who obtained the figures, said Mr Khan was right to highlight the problem but added: “His actual record of delivery has been pitiful. There is a huge gulf between his words and actions.
“Over a period of more than 20 months he has provided childcare help for just 35 employees.
“Sadiq Khan is constantly calling for action from everyone else. It is about time that he looked at his own record as Mayor of London and ensured all staff are aware and able to take up childcare loans within the organisations he runs.”
There are more than 75,000 employees working directly for organisations controlled or directed by Mr Khan, according to official figures.
As of April this year, not a single employee from the London Fire Brigade, the Mayor’s Office for Policing and Crime and the London Legacy Development Corporation had taken up the offer.
London is the most expensive region in the UK for childcare with parents paying around £9,100 per year for a part-time nursery place for a child under two, compared to a national average of £6,600, according to Coram Family and Childcare trust.
The costs stop many parents from starting a new job or returning to work with nurseries and childminders regularly charging up to £1,500 in upfront fees and deposits.
A spokeswoman for mayor said: “We promote the scheme to staff but are committed to doing more to raise awareness of it.
“The Mayor is encouraging other employers to follow his lead and has produced guidance on how to implement this scheme and included it in his Good Work Standard.”
City Hall said the scheme was promoted at staff benefits fairs, on the Women’s Network and on the intranet.