Massachusetts Governor Deval Patrick has given final approval to legislation that seeks to prevent home foreclosures by forcing mortgage lenders to offer modifications on certain ‘‘risky’’ loans.

Patrick signed the bill Friday afternoon. It had passed unanimously in both chambers of the Legislature.

The governor said the legislation creates ‘‘unparalleled consumer protections.’’

It requires lenders to assess a borrower’s circumstances and determine whether the net value in changing an existing loan is more than the anticipated recovery from foreclosure. If so, the lender is required to offer a loan modification to the borrower.

It also prohibits lenders from foreclosing on properties without proper documentation and includes provisions to create a task force to study mediation programs.