Rates on Help to Buy Isas have plummeted since launch, research from Which has found.
The consumer testing group said more than half of providers have slashed their rates since Help to Buy was launched in 2015, when it was possible to get rates of four per cent.
Which analysed 23 providers, and shamed Halifax as the provider who had slashed rates the furthest, a drop of 1.75 per cent to 2.25 per cent.
The vast majority of best buy rates are now only available from small providers in certain areas, with a 2.56 per cent rate from Newcastle Building Society the highest widely available rate.
Halifax recently changed the rates for all Help to Buy customers to 2.25 per cent - a significant cut for those who were enjoying rates of 3.5. per cent and had enjoyed a four per cent rate at launch.
Halifax said it was simplifying its range, and some customers would be getting a higher rate than before.
According to Which, those banks and building societies that had raised rates were those who had started off below market rate and said there was no Help to Buy Isa offering a market leading rate at present.
Using a Help to Buy Isa, customers saving for their first home get a bonus from the Government of 25 per cent - the maximum government bonus is £3000 per person and the ISA is only available to first-time buyers.
However, customers can now choose between it and a Lifetime ISA, or Lisa, which has a similar bonus but allows them to save £4000 a year, with £1000 from the government.
Lisas can be opened by those under 40 and those under 50 can save into them. The money can be used for a first home or taken after the age of 60 as retirement savings. Customers can transfer savings from a Help to Buy ISA into a Lisa.
