The number of accounts paying introductory bonuses has soared, as banks and building societies try to lock savers in for a set period or curb flexibility.

The average short-term bonus on the best deals has risen to 0.9 per cent – higher than the average instant access rate of 0.7 per cent, research from MoneyExpert.com, the financial comparison website, shows.

Some 21 per cent of products in the savings market now offers some form of special conditions compared to 16 per cent a year ago. The average bonus size has grown in the past year by 0.2 percentage points while the average instant-access savings rate has tumbled by 2 percentage points.

Pierre Williams, head of research at MoneyExpert.com, said: “Beggars can’t be choosers and given the low rates nowadays savers are effectively beggars when average rates are just 0.7 per cent. Bonuses are no bad thing and given the state of the market savers may just have to play ball.”

However, he said those who wanted the top rates would have to work hard to achieve them.

“The way things are going we could be sliding into a situation, such as we have in the credit card market, with customers jumping from one product to the next desperately chasing any decent rate.”

On top of bonuses, providers are also finding other ways to inhibit flexibility. The average minimum deposit required to net the best rates has increased from £986 a year ago to £1,263 now – up 28 per cent. What’s more, some providers are attempting to keep that money by offering bonuses to those making a limited number of withdrawals. The Advantage Private Reserve account from NatWest, for example, includes a 0.25 per cent bonus for customers not making any withdrawals in a given month.