"Savers may assume that they will benefit from last week’s Bank of England base rate rise within the next few weeks by default, but as we have seen before, this is not guaranteed."
Variable savings rates for children will also increase by 0.25%, but all other variable rate savings accounts will increase by just 0.10%.
Interest rate increases for borrowers and savers will come into effect on 1 September 2018.
Research from Moneyfacts, published yesterday, found that even if the biggest brands were to pass on the full 0.25% rise, their easy access accounts will still fail to match or beat 0.75%.
Rachel Springall, Finance Expert at Moneyfacts, said: “Savers may assume that they will benefit from last week’s Bank of England base rate rise within the next few weeks by default, but as we have seen before, this is not guaranteed.
“In November 2017, it took around a month before most savings providers passed on the rise, and at the same time, some brands were selective with which accounts to improve. As an example, savers who held a First Direct bonus saver with a low balance received a rise of just 0.10%. Halifax raised some accounts by 0.15% and HSBC only added 0.20% to its online bonus saver, and still offers an account paying just 0.05%. All three brands were quick to pass on a 0.25% rise to their mortgage customers however, with their SVRs changing at the start of December 2017."