Proposals for a £205-a-year increase in bills are higher than the previous suggestion of a 44pc increase put forward by Thames Water in April.
The company said the main driver of the rise was “an update to our customer numbers which [had been reduced] from our original plan”, as well as previously forecast increases in spending.
Mr Weston said: “We want to deliver a considerable increase in investment in our infrastructure, with total expenditure of £20.7bn in our core plan and a further £3bn through gated mechanisms.
“The money we’re asking for from customers will be invested in new infrastructure and improving our services for the benefit of households and the environment. They are not being asked to pay twice but to make up for years of focus on keeping bills low.”
A water industry body warned that Ofwat’s plans to cap water bills could create a “material risk” that suppliers may fail to raise enough cash to invest in stopping sewage leaks.
Trade association Water UK said Ofwat’s draft plans to limit the rise in household water bills to £19 a year on average would hold back firms’ abilities to improve services.
In a letter to David Black, Ofwat’s chief executive, the group warned that the bill cap would drive away the investors needed for a multi-billion-pound plan to bring Britain’s water infrastructure up to scratch.
David Henderson, of Water UK, wrote: “Ofwat’s approach would make it impossible for the water sector to attract the level of investment that it needs and will reduce the UK’s attractiveness to international investment.”