The product will be available from 2 June at 60 per cent loan to value (LTV) with a £1,499 fee.
The lender has also reduced rates on its residential range and re-introduced a three-year fixed product.
The three-year fixed mortgage is at 80 per cent LTV and has a rate of 2.65 per cent. It has no fee and offers £1,000 cashback.
The five-year fix at 60 per cent LTV with £250 cashback and a £1,499 fee has been reduced from 1.24 per cent to 1.18 per cent. The equivalent at 85 per cent LTV has been cut from 2.71 per cent to 2.67 per cent.
Fred Sharp, director of mortgage distribution at Platform’s parent company, The Co-operative Bank, said: “We’re committed to offering competitive deals to borrowers who are in the market for a good value mortgage product for their circumstances.
“We’re reducing the interest rates on a number of our on sale mortgages to support buyers within all stages of the housing ladder and also offering up to £1,000 cashback on select mortgages to help ease the cost of buying a property for aspiring homeowners or home movers.”