OTTAWA -- Child care advocates are questioning the federal government's claim that an increase in its cornerstone child benefit will make daycare more affordable.

Liberal ministers have been making the claim to promote the plan, unveiled in Tuesday's economic update.

Child care groups say the extra cash will help families pay the bills, but cite research that shows such cash payments to parents don't make child care cheaper or more available to families that need a space.

The Liberals plan to increase the Canada child benefit next July to keep pace with inflation, something they previously said they wouldn't do until after the 2019 election.

Federal coffers are expected to dole out an extra $5.6 billion over five years, raising the annual cost of the program to about $25.2 billion by 2023, up from $23.2 billion budgeted for this fiscal year.

Don Giesbrecht, CEO of the Canadian Child Care Federation, says the Liberals appear to be emphasizing the benefit as a way to defray daycare costs, rather than promoting $7.5 billion over 11 years the government plans to give to provinces to fund child care spaces.