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National Savings and Investments has boosted rates on a number of savings accounts, launching them up the best buy tables.

New issues of fixed-term British Savings Bonds (also known as Guaranteed Growth, and Guaranteed Income Bonds) pay up to 4.5 per cent.

NS&I says the move 'reflects changes in the wider market' and will help it meet its net financing target.

In recent weeks, savings rates have been nudging higher, with the top one-year fix in the independent This is Money savings tables paying 4.66 per cent, from MBNA.

The overall best fixed rate is 4.7 per cent from Market Harborough Building Society, but requires locking money away until 2031.

Meanwhile, yesterday, Skipton Building Society launched a new cash Isa best buy, paying 4.55 per cent.

Today, NS&I has upped the rate on its one-year bond to 4.5 per cent, up from 4.07 per cent. On the monthly income version, the rate has risen to 4.41 per cent.

This is the best overall rate NS&I now offers. It has also boosted its two year fix to 4.48 per cent, three year to 4.45 per cent and five year to 4.4 per cent.

On the monthly income options, the rates are 4.4 per cent, 4.37 per cent and 4.32 per cent respectively.

Funds cannot be withdrawn early with these fixed-term accounts. They require a minimum of £500 to open and savers can put in a maximum of £1million, backed by the Treasury.

This is an attraction for wealthier customers with big savings pots, as banks and building societies – under the Financial Services Compensation Scheme – give protection at a slimmer £120,000, meaning splitting cash for full protection.

The accounts are available to new customers, and those with existing bonds set to mature.

In addition, NS&I has boosted the rate on one of Britain's worst accounts. 

Often flagged by This is Money as a dud, the Investment Account – a postal only account – will see the rate rise from 1 per cent to 2.05 per cent.

All other NS&I savings products are untouched today. From the April draw, the Premium Bonds underlying rate fell to 3.3 per cent while Income Bonds remain at 3.01 per cent.

For those who want to take a monthly income, the one-year fix is now likely to be a better option, unless you need easy-access to the cash.

Besides Premium Bonds, all of these accounts are taxable, so it is worth factoring this in and utilising your Isa limit.

NS&I hasn't touched its tax-free Direct Isa account, which currently pays 3.5 per cent.

NS&I has 24million customers and its net financing target for this financial year is £15billion, give or take £4billion. 

With competition ratcheting up, it could mean more rate rises are required by NS&I to attract the cash it requires.