After Thursday's win over Bosnia and Herzegovina, Judy Murray's team were given a tougher examination by Portugal.
Robson, who won Olympic mixed doubles silver with Andy Murray at London 2012, beat Margarida Moura 6-2 6-1 before Heather Watson lost 6-1 6-4 to Michelle Larcher De Brito.
However, Robson and Watson combined to win their doubles encounter over Larcher De Brito and Joana Vale Costa 6-2, 6-1 for a 2-1 victory for Britain.
Murray's team will now face Hungary in their final pool encounter on Saturday and another win on Sunday would see them advance to the World Group II play-offs in April.
- Sports & Recreation
- Andy Murray
- Michelle Larcher De Brito
- Judy Murray
- Heather Watson