The lender has cut rates across its range by up to 0.70 with buy-to-let rates starting at 11.45%.
Loan to values have also been increased with buy-to-let loan to values now available up to 70%.
Stuart Aitken, chief operating officer at Masthaven, said: “These improvements are a further decisive step as we carefully build a substantial presence in the market.
“We are delighted to again include improvements that result from conversations with our broker partners. MSL will continue to roll out new and innovative products throughout this year.”
Richard Keen, head of intermediary development at The Loans Engine, said: “As the rental sector remains strong, brokers are recognising an increase in demand from investors looking to raise additional finance against their residential investment properties.
“The new BTL enhancements from Masthaven are a positive step to meet this demand. As many buy-to-let mortgages carry a substantial tie-in, landlords would therefore have to pay an excessive redemption penalty in order to raise additional funds via remortgage.
“Buy-to-let secured loans offer a viable solution for those landlords needing to raise finance without disturbing their current buy-to-let offering.
“Overall, these product changes will give borrowers some considerable leeway and we’re delighted to provide our brokers with access to these substantial enhancements.”