Over £57.3bn was invested in adult Isas during 2012/13, according to HM Revenue and Customs.
This was an increase from £52.7bn in 2011/12 and was divided £40bn into cash Isas and £16bn into stocks and shares Isas.
Figures were released by HMRC today on the number of Isas for the 2012/13 tax year.
The average amount saved per account was £3,935, up from £3,756 last year. The Isa limits are £5,760 for a cash Isa and £11,520 for a stocks and shares Isa.
Some 14,599 adult Isas were opened in 2012/13, up from 14,049 in 2011/12.
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For Junior Isas, 295,000 were opened in 2012/13, an increase from 71,000 in 2011/12. This was split between 203,000 in cash Isas and 92,000 in stocks and shares Isas.
Junior Isas were introduced in November 2011 as a replacement for Child Trust Funds and all children under 18 are eligible so long as they do not already have a Child Trust Fund.
Over £392m had been saved into a Junior Isa, up from £115m in 2011/12. Some £293m of this was saved into a cash Isa while £99m was in a stocks and shares Isa.
The average amount saved per account was £1,327, a decrease from £1,623 the previous year.

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