responsible for, responsible to

The adjective responsible can be followed by the prepositions for or to.

Use for when you are naming a task that a person or group has to carry out:

• We are responsible for the program.
• Marian is responsible for overseeing the project.
• Greg was responsible for that.

Use to when you are naming the person or group of people to whom you have a duty:

• The company president is responsible to the Board of Directors.
• We are responsible to our clients.

Both to and for may be used together:

• We are responsible to the client for the accuracy of the report.
  [i.e. We have a duty to the client to ensure that the report is accurate.]