Customers can transfer their Help to Buy Isas into the One Family Lifetime Isa, which could potentially give them an extra bonus for their savings, so long as the transfer happens before 5 April this year.
Lifetime Isas, or Lisas, are available to anyone aged less than 40 and can be used to save for retirement or for a new home provided that you are a first-time buyer.
For every £1,000 saved the government will add an additional bonus of £250, up to £1,000 per year.
This year only, any cash you hold in your Help to Buy Isa before 5 April 2017, including interest earned on that cash, can be transferred over to a Lifetime Isa without it counting towards the yearly £4,000 Lisa allowance.
The One Family Lifetime Isa can be opened with just £250, or with a £25 a month direct debit.
There is an annual management charge of 1 per cent.
The two different funds have differing risk levels, with one invested mostly in corporate bonds, and the other mostly invested in shares.
Customers can switch between the two at any time.
Nici Audhlam-Gardiner, managing director of One Family, said: "We are delighted to be entering the Lifetime Isa market.
"Our Lifetime Isa provides much needed additional help for 18 to 39-year-olds, who, with the increase in the cost of living and stagnant wages, are finding it harder to save for their first home or for retirement.
"Opening online takes 10 minutes and can be done via a mobile phone."
However, financial adviser Carl Roberts said the 'moderate' fund, which One Family stated could be used if you are planning to invest for five years or more, can have up to 40 per cent in equities.
Mr Roberts said: "I wouldn't say that was appropriate for someone only investing for five years.
"Especially if they want to maximize their house deposit."
Alistair Cunningham, financial planning director at Wingate Financial Planning, said: "The lack of choice is woeful across the whole sector. You can count on the fingers of one finger how many providers offer something genuinely open architecture that can be used for bona fide lifetime savings.
"I think there is a perception that Lisas are only for first-time home buyers and therefore are not worth manufacturing.
"I think this is nonsense as a Lisa can be a great mortgage repayment vehicle with the government effectively helping to pay back 20 per cent of the capital cost of an interest-only mortgage at 60 or later."
Alan Chan, director and chartered financial planner at London-based IFS Wealth & Pensions, said with only two funds available the OneFamily offering "does lack flexibility and choice" but added it is "simple for those who choose go direct".
He said: "A 1 per cent charge seems fair for this kind of account."
One Family was formed from the merger of Family Investments and Engage Mutual.
It announced in February last year that it was exploring the Lifetime Isa market.
There have been growing concerns that the Lisa could be the next mis-selling scandal on the horizon - as predicted by Ros Altmann, former pensions minister, back in 2016.
She warned the Lifetime Isa isn’t even close to being as beneficial as a pension post retirement freedoms.
Baroness Altmann said: “In my view Lifetime Isas risk poorer pensioners in the future and it is a disaster in the making.
“This product has mis-selling written all over it. Just think about it from a customer’s perspective. The Lifetime Isa isn’t a simple product. It needs somebody to understand the whole environment."
