Sales of Junior ISAs (JISAs) soared in 2012-13, government figures show.
Some 295,000 new accounts were opened in the tax year - with a total of £392m invested - compared to the 71,000 sold in the six months following the products' launch in November 2011.
However, the average amount invested has gone down from £1,623 to £1,327 in the same period. Family and friends can invest up to £3,600 tax free into the products.
Junior ISAs replaced Child Trust Funds (CTFs), which were savings accounts for children born between 1 September 2002 and 2 January 2011 and included free cash vouchers of up to £250 given out by the government.
The Treasury is currently consulting on allowing the transfer of savings from a CTF account into a JISA. The consultation closes on 6 August.
Danny Cox, head of financial planning at Hargreaves Lansdown, said: "Junior ISAs seem to be gaining some momentum which will be improved once transfers are allowed from Child Trust Funds. Allowing transfers would seem far more likely to go ahead than an all-out merger and doing nothing is not a realistic an option."
Meanwhile, sales of adult ISAs also increased, with 14.6 million new accounts opened in the 2012-13 tax year compared to 14.2 million in the previous 12 months.
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