This is the third time the Post Office has trimmed rates on this product since its launch last November at a rate of 6.09 per cent.
However the product is only available to borrowers in the North of England as part of the Post Office's current mortgage trials.
Fees remain the same at £399 for arrangement and no HLC, with the LTV sticking at 95 per cent.
Rates on its three year fixed buy-to-let and self-certification mortgages have also been cut to 5.99 per cent.
Director of lending at the Post Office, Gary Fitton, said: “These new rate cuts put our mortgage range at the top of the comparison tables, further proving our commitment to offering customers transparent and excellent value for money products."
Post Office mortgages are provided in conjunction with Bristol and West.
