The "bank of mum and dad" contributes around £17,000 to help first-time buyers raise the £28,000 deposit typically needed, equating to £2 billion added to the UK housing market each year from parents, Shelter said.
The yearly estimate is almost double the average of £1.1 billion spent annually by the Government on its affordable homes programme in England, according to the charity.
Shelter said the findings show that the younger generation's struggle to get on the property ladder is still putting a strain on parents' finances, despite recent Government schemes to unblock the housing market and give people with smaller deposits a leg up.
More than a quarter (27%) of first-time buyers are still reliant on parents to help them raise a deposit, compared with less than one fifth (17%) before the financial crisis struck, according to the findings.
One fifth of parents said they had been forced to save less for their retirement to help fund their children's mortgage deposits and one quarter were cutting back on their own spending.
The Council of Mortgage Lenders (CML) recently reported that first-time buyer numbers lifted in May to their highest levels in five-and-a-half years.
Help to Buy will be fully launched next year and will see the state offering guarantees to enable £130 billion-worth of low-deposit mortgage lending. But with house prices already rising faster than expected this year, concerns have been raised that the scheme could fuel a property bubble and encourage people to over-stretch their finances.
Despite the financial downturn, house prices have remained high by historic standards when compared with wages.
Campbell Robb, chief executive of Shelter, called for the Government to do more to fix the "broken housing system".
He said: "The fact that the bank of mum and dad has to play such a central role in our housing market shows just how desperate the situation has become for a generation that's priced out of a home of their own.
"Something is seriously wrong when people who work hard and save each month still have no hope of buying a home without significant financial support from their parents.
"And while parents want to help their children to get a start in life, with the growing squeeze on family budgets the reality is that the majority can't afford to."
More than 15,000 people took part in the research.
Housing Minister Mark Prisk said: "Shelter's report fails to take into account the 170,000 new affordable homes we'll have built by 2015, or the £3.3 billion we're investing to provide a further 165,000 new homes in the three years to 2018 - leading to the fastest annual rate of affordable housebuilding for two decades.
"On top of this our Help to Buy scheme is offering a valuable alternative to the bank of mum and dad, by enabling people to buy newly-built homes with just a fraction of the deposit they would normally require.
"In just three short months, we've seen over 1,000 sales and nearly 7,000 reservations and developers confirming that this surge in demand is leading them to build more homes."