An amendment put forward by the Labour peeress Baroness Hollis, with backing from Tory ex-minister Baroness Young, will force a divorced husband to pay up to half his pension to an ex-wife when he retires.
A further amendment laid the obligation with the pension schemes themselves to divide the pension and make payments to the former wife.
Government had planned to leave this responsibility with the husband. But Baroness Hollis warned that this would increase the burden of litigation going through the courts.
Now, she said, payments "would flow securely to the wife without asking an elderly woman of 75 to pursue her husband as a litigant through the courts, clogging up the system, demanding legal aid and causing immense and unnecessary distress to all parties".
Peers also voted against the Government to restore pensions to war widows, if widowed for the second time, or divorced.