The mortgage guarantee scheme is expected to expire at the end of 2016, but 65% of lenders believe competition in the high loan-to-value sector will decrease if it is not replaced or extended.

The study by the Intermediary Mortgage Lenders Association (IMLA) also found three-quarters of mortgage brokers shared similar concerns.

It also asked lenders and brokers what impact any market intervention by the Bank of England’s Financial Policy Committee could have. Some 40% of banks and building societies said scaling back of Help to Buy was the most likely option, an opinion shared by 51% of brokers.

But both groups were fearful of such actions, just 14% of brokers and 10% of lenders said this would benefit the market.

Peter Williams, executive director of IMLA, said with home ownership among young people falling, any changes to the schemes would need to be carefully considered.

“The Help to Buy mortgage guarantee has breathed new life into the market and opened the door to more prospective homeowners without sacrificing standards when it comes to affordability checks,” he said.

“It is encouraging to see more lenders offering 95% LTV products outside of the scheme – but it would be a big gamble to rely on this continuing without the boost that the government has brought to the first time buyer market.

“Homeownership continues to fall, especially among younger adults, and letting Help to Buy expire without a permanent replacement will be another nail in the coffin of the ambitions of many people to own their own home.”