Harry Kane scored his ninth Premier League goal of the season but Tottenham's dwindling title hopes were dealt another blow as managerless West Brom left Wembley with a 1-1 draw.
Salomon Rondon gave Albion and their unheralded caretaker manager Gary Megson an early advantage five days on from Tony Pulis' sacking.
The visitors looked set for a first league victory since August until their massed defensive ranks were punctured by a typically expert piece of movement and poaching from Kane in the 74th minute.
A winner proved elusive and Mauricio Pochettino – who once again raised eyebrows pre-match by omitting Danny Rose from Tottenham's matchday squad – has presided over a solitary league victory in his past four attempts.
Spurs fall five points behind second-placed Manchester United, while leaders Manchester City will be 13 points better off if they can beat Huddersfield Town on Sunday.
A dispiriting week meant West Brom – who edged a point clear of the relegation zone - emerged at Wembley with few expectations but they stunned the majority of those inside the national stadium after four minutes.
Dele Alli was caught napping in midfield by fellow England international Jake Livermore, who fed Rondon to outmuscle Davinson Sanchez and smuggle a finish beyond a static Hugo Lloris and into the bottom left corner.
Tottenham's response lacked fluency or purpose, with Kane belatedly involved in the 27th minute when he turned Ahmed Hegazi and scuffed wide from the edge of the area.
Ben Foster pushed to safety after Son Heung-min's drive took an awkward bounce in front of him and the West Brom goalkeeper held on to Eric Dier's header from Kieran Trippier's outswinging corner.
Son established himself as Spurs' most threatening attacker during the closing moments of the first half – flashing a teasing low cross just beyond Kane before having a shot deflected on to the roof of the net in stoppage time.
Kane shot goalwards from outside the box shortly after the restart but was off balance, making Foster's task easier than it might have been.
West Brom retained an occasional threat on the break and Rondon cut in from the right in the 55th minute to lash a powerful strike past the far post.
Spurs' play remained ragged and Dier was a symbol of their frustrations before the hour when he was booked for persistent dissent.
Alli flung himself in at the back post in vain when Trippier's volley into the turf skidded across goal in the 68th minute.
Six minutes later, Alli turned provider and left the poaching to Kane, who expertly guided his low cross home to lift the Spurs faithful out of their bubbling frustration.
The England striker was suddenly leading Tottenham's charge and tumbled on the edge of the area under a desperate Livermore challenge. Christian Eriksen – unusually ineffective for the hosts – fired the resulting free-kick into the wall.
Kane was crowded out by West Brom defenders as he tried to head in from a Trippier cross and, despite the rousing win over European champions Real Madrid at the start of this month, Wembley still does not quite feel like home for Tottenham.
Albion substitute Hal Robson-Kanu almost supplied a sting in the tail during stoppage time when he blasted a volley at Lloris before tearing down the right flank and seeing Rondon touch his dangerous delivery wide.