Retained EU Law (Revocation and Reform) Bill

The Minister speaks for Defra and assures the Committee that the Government are entirely committed to progressing environmental standards and will follow international law. Why is there any problem putting a non-regression clause and an agreement to follow international law in the Bill if that is what the Government plan to do anyway? Further to that, can the Minister assure me 100% that before the next general election there will be no change of direction in the Government, change in Prime Minister or change in ministerial personnel?