According to a survey by CoreData, 34 per cent of those planning to invest in the Lisa will cut the amount of money they put into their pension, while 7 per cent will stop saving into it altogether.
The findings will prompt growing concerns that the Lisa could be the next mis-selling scandal on the horizon - as predicted by Ros Altmann, former pensions minister, last September.
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."
Nearly half of the 267 people polled by Coredata between March and April 2017 who said they were planning to invest in the Lisa said they will not alter their pension contributions as a result of putting cash into the Lisa.
A pension is tax-free when you pay into it - so the taxman contributes an extra 25 per cent to the amount paid in by basic rate taxpayers - but money taken out after the age of 55 is taxable.
A Lisa is the exact reverse. You will have already paid tax on contributions into it, but money taken out will be tax-free.
The Lifetime Isa has been available since April for those aged 18 to 40, giving them a new option when it comes to saving for their first home or topping-up their pension savings.
With a Lisa, they will be able to save up to £4,000 a year and benefit from a government bonus of £1 on top of every £4 saved.
The bonus takes it up to £5,000 a year.
But there is a sting in the tail as you need to use the proceeds to buy your first home or take your savings after age 60 to keep your bonus otherwise there is a 5 per cent exit penalty and charges, as well as a loss of growth on the added bonuses.
Craig Phillips, head of international at CoreData Research, said the findings of his survey add weight to the view that the Lisa could accelerate a shift in the retirement landscape away from pensions and toward Isas.