Doubts have been raised as to how widely available Lifetime Isas will initially be when the products start launching from next month.
Several major savings providers said they have no immediate plans to launch Lifetime Isas, with some still going over the details or waiting for finalised rules.
But the Treasury said it expected the market to continue to grow, with more providers coming on board as products were developed.
Lifetime Isas will be made available to the under-40s to open from April 6, to help them save up to £4,000 per year for their first home or their retirement, with a 25% Government bonus.
Over their lifetime, savers could potentially get a maximum bonus of £32,000. Savings can be used to buy a first home, or used for other purposes after the saver reaches 60. But generally, savers withdrawing their money early for reasons other than buying their first home will face withdrawal charges.
Experts have raised concerns that some savers may ditch their workplace pension, which gives them the benefit of employer contributions, in favour of saving into a Lifetime Isa.
Former pensions minister Baroness Altmann told the Press Association: “It is very difficult to see people being better off saving for later life with a Lifetime Isa, rather than a pension.”