She argued that there is “no plan” behind the Government’s pledge of 30 hours of free childcare, and parents will be left “bitterly disappointed”.
But Labour is yet to give details of its rival blueprint to help millions of parents struggling to afford childcare.
Chancellor Jeremy Hunt, in his March Budget, laid out proposals that would see 15 hours of care extended to all children over the age of nine months from September next year.
Working parents of children under five will be entitled to 30 hours per week from 2025.
Applications for parents to register their children for the first raft of reforms open on January 2, the Government announced this week.
Ms Philipson told the Standard: “What the Conservative government have set out in terms of their policy has no plan behind it, to deliver on workforce, or to create the places that parents will need.
“That’s why I’ve asked [former Ofsted Chief Inspector] Sir David Bell to lead Labour’s early years review in these areas, because without the skilled workforce and without the places desperately needed in London and across our country, parents will feel bitterly disappointed by the Government’s promises that they have no plan to deliver on.”
The number of childcare places has dropped by 24,000 in the past financial year, according to the National Day Nurseries Association.
Ms Philipson said Labour would "reform the system" to deliver "childcare opportunities from the end of parental leave to the end of primary school" starting with universal free breakfast clubs
"That would make a massive difference to families in London and across our country who are battling with cost of living pressures," she said.
In a bid to get more staff into the profession, the Government is offering childminder start-up grants of £600 for those who register with Ofsted and £1,200 for those who register with a childminder agency.
Applications launch on Thursday.
Education Secretary Gillian Keegan said: "Our fantastic childcare offer is going to start supporting eligible families in less than six months' time, and I want to make sure that parents and providers are prepared."
"From April next year, eligible working parents of two-year-olds will be able to access 15 hours of government-funded childcare a week, making sure parents no longer have to choose between a career and a family, and doubling down on this government's commitment to getting more people into work and growing the economy."