Jurgen Klopp's side are now a whopping 16 points ahead of second-place Leicester City – who lost to Southampton earlier in the day – although their lead at the summit could be cut to 14 points if Manchester City overcome Aston Villa on Sunday.
The Reds were dominant in the first half and made the most of their superiority when Firmino expertly drilled home from inside the penalty area after 37 minutes.
Son Hueng-min and Giovani Lo Celso squandered golden opportunities to snatch a scarcely deserved point for Jose Mourinho's men late on, with Liverpool ultimately holding on for yet another three points.
BIG WIN! https://t.co/JbUsCmD0Ar— Liverpool FC (@LFC) January 11, 2020
Liverpool twice came agonisingly close to going ahead inside two minutes. Firmino's initial effort was cleared off the line by top-flight debutant Japhet Tanganga, with Alex Oxlade-Chamberlain lashing against the post from the follow-up.
Lucas Moura, Son and Dele Alli all missed the target from promising positions soon after, while at the other end Virgil van Dijk headed straight at Paulo Gazzaniga from just six yards.
There was little the Spurs goalkeeper could do to deny Firmino eight minutes before the interval, the Brazil international controlling Mohamed Salah's pass with a sublime touch before lashing in from 10 yards.
Spurs started the second half with a spring in their step and twice came close before the hour mark, with Serge Aurier testing Alisson and Son seeing an effort deflected narrowly wide.
The game was almost put out of their reach in the 66th minute but Gazzaniga got down sharply to paw away Sadio Mane's header.
Spurs rallied in the closing stages, with Son blazing over from a glorious position and substitute Lo Celso somehow diverting Aurier's cross wide from inside the six-yard box seven minutes from time.
Klopp was visibly furious at his side's defending, but it mattered little in the end as they held on for a win that strengthens their already formidable position at the summit.
What does it mean? Relentless Reds march on
Klopp's men have now taken a scarcely believable 88 points from their last 90 available in the Premier League, winning their last 12 matches in a row.
They rarely looked in danger of failing to claim all three points against a Spurs side desperately missing the presence of the injured Harry Kane in attack.
Mourinho, meanwhile, needs to turn his side's fortunes around sharpish. They have now won just one of their last five Premier League games and are nine points behind fourth-place Chelsea.
Firmino's touch of class
Mane and Salah often steal the headlines, but Firmino once again proved his worth with a superb goal. His first touch was exquisite, and the finish was not bad either. He also created four chances for his team-mates.
Eriksen's Spurs career ending with a whimper
With a move to Inter seemingly on the cards, it was a surprise to see Christian Eriksen named in Mourinho's starting XI.
Despite creating a few chances, he failed to repay his manager's faith, serving up a dismal display where he was often outmuscled and appeared to be lacking intensity.
What might be one of his last appearances in a Spurs shirt ended with a 69th-minute substitution.
Key Opta Facts
- Liverpool have collected 61 points in the Premier League in 2019-20 - the most any side has ever registered after 21 games in a single season across Europe's big five leagues (assuming three points for a win).
- They have accrued 104 points across their last 38 Premier League matches (W33 D5 L0); this is a record total by any team across a 38-match spell in the competition’s history, overtaking 102-point stretches by Man City (ending in 2018) and Chelsea (2005).
- Tottenham have conceded 20 goals in 13 matches in all competitions under Mourinho; it took Mourinho’s Chelsea side 44 games before shipping their 20th goal during his first spell in England as a manager in the 2004-05 season.
- This is Liverpool's joint-best scoring run from the start of a season in English top-flight history, with the Reds also scoring in their opening 21 games in 1933-34.
- Liverpool have now gone 38 Premier League games without defeat (W33 D5); since their last league loss at Manchester City in January 2019, Tottenham have lost 16 Premier League matches by comparison, including three to the Reds.
- Tottenham have lost back-to-back Premier League matches for the first time this season, having last done so in May 2019, while this is the first time their manager Mourinho has lost consecutive games in the competition since August 2018 as Manchester United boss.
- Liverpool have kept six consecutive clean sheets in the Premier League for the first time since December 2006 (seven).
- Firmino has scored five goals in his last six games for Liverpool in all competitions, as many as he had in his previous 30 appearances for the Reds before this run.
Tottenham host Middlesbrough in an FA Cup third-round replay on Tuesday before visiting Watford in the Premier League on Saturday. Liverpool, meanwhile, welcome bitter rivals Manchester United – the only side they have dropped points against this season – to Anfield on Sunday.