The savings would come from reducing the incidence of common childhood diseases and curbing the subsequent risk of breast cancer in the mums, all of which have been linked to low rates of breastfeeding, say the researchers.
The numbers add up to a strong economic case to invest in services to support mums to carry on breastfeeding, they conclude.
In common with many other high income countries, breastfeeding rates in the UK are low, and to find out if boosting these could cut healthcare costs by improving mother and child health, the researchers focused on five priority diseases.
They looked at the financial impact of not breastfeeding on gastrointestinal and lower respiratory tract infections; the ear infection otitis media in infants; the potentially lethal gut disorder necrotising enterocolitis in preterm babies; and lifetime risk of breast cancer in mothers.
They calculated the annual cost of treating the four childhood illnesse as £89 million, and the lifetime costs of treating breast cancer in women who had given birth as £960 million (at 2009-10 values).
They then applied a rigorous seven step framework to their analysis, to calculate how much of these costs could be saved by extending the period of breastfeeding.
They worked out that helping women who exclusively breastfeed for 1 week to keep going for at least 4 months could save at least £11 million a year by cutting the incidence of three infections.
Additionally, doubling the rate of breastfeeding in neonatal units from 35% to 75% could lop an extra £6 million off the annual NHS bill for treating necrotising enterocolitis, they say.
And doubling the proportion of mums currently breastfeeding for between 7 and 18 months would likely cut the incidence of breast cancer in these women and save at least £31 million, they calculate, as well as improving their quality of life.
The researchers emphasise that achieving the savings they envisage does not depend on persuading more women to breastfeed. Rather, it hinges on helping those who have already chosen to do so, to extend the overall duration of breastfeeding.
This means actively supporting them with accessible high quality services, they point out. "This is very important because national statistics indicate that 80% of women who stop breastfeeding in the early weeks would have liked to have breastfed for longer," they write.
There is therefore a strong economic case for investment in these services, they say.
"Our study should reassure policymakers, service planners and commissioners that a rapid return on investment is realistic and feasible, supported by cost savings that can be realised in the first year of infants' lives," they conclude.