The lender is offering a two-year fixed rate at 4.95% and a five-year fixed rate at 5.35% both with no arrangement fee.
John Willcock, head of Post Office Mortgages, said: “2014 is already proving to be an exciting year for Post Office mortgages and we are pleased to announce our competitive Help to Buy rates as part of this.
“By strengthening our mortgage business and offering buyers the opportunity to purchase a property in the way that best suits their needs we hope to consolidate our position as a leading player in the market.”
In January the Post Office announced its ambitions to become one of the top 10 mortgage lenders in the UK in 2014.
Ahead of the implementation of the Mortgage Market Review on 26 April the lender plans to increase its in-branch qualified advisers to 100.