Northern Rock has launched one, two and three-year cash Isas that savers manage online.

The one-year deal pays a tax-free 3.35 per cent fixed until 24 January 2013 and you can put in new money and move your current cash Isas into the account.

It makes it the top one-year deal. Leeds Building Society pays a decent 3.25 per cent but you can only put this year’s £5,340 cash Isa allowance into the account as it does not accept transfers from other providers.

Northern Rock’s two-year deal pays 3.75 per cent, also a competitive rate now that Cheshire, Derbyshire and Dunfermline building societies, all part of Nationwide, have withdrawn their two-year fixed-rate deals at 3.75 per cent.

Its three-year cash Isa pays a top 4 per cent while Halifax now pays 4.3 per cent for four years.

On taxable fixed-rate bonds, AA Savings now pays a top 3.6 per cent before tax (2.88 per cent after tax) for one year. Close Brothers' two-year bond at 4.25 per cent (3.4 per cent) has been withdrawn from sale leaving Cahoot, part of Santander, at 4.01 per cent (3.21 per cent) as the top deal.

Which Money has warned savers to ensure they are in decent paying variable rate accounts. Its research reveals there are 733 accounts paying 0.5 per cent or less before tax, including those now closed to new savers. The figure is 23 per cent up on the 595 accounts this time last year.