A mother and daughter "filled with hate and toxic ideology" have been jailed for planning terrorist attacks in London, including a likely knife rampage.

Rizlaine Boular, 22, and her mother Mina Dich, 44, had earlier admitted preparing terrorist acts after having been tracked by police as they drove around carrying out reconnaissance of potential targets in central London in April last year.

The following day, the pair went to a supermarket in Wandsworth, southwest London, where they bought a pack of three kitchen knives, police said.

After their arrest, detectives recovered electronic devices from both Rizlaine's and Mina's address, on which they found Islamist extremist content.

"(They) were filled with hate and toxic ideology and were determined to carry out a terrorist attack," said Deputy Assistant Commissioner of London police Dean Haydon.

"Had they been successful, it could well have resulted in people being killed or seriously injured," he added in a statement.

Boular was sentenced on Friday at the Old Bailey court to life imprisonment with a minimum term of 16 years. Dich received an extended sentence of 11 years and nine months.