Played in front of over 1,700 fans, Spurs had a goal disallowed, lost to a penalty and did just about everything but score but as manager Karen Hills admitted: "It was wasn't our night."
Lucia Leon was denied by the assistant's flag as the team dominated for long periods only to lose out to Katie Bottom's spot-kick on 69 minutes.
"The biggest disappointment is that the performance wasn't a true reflection of our season," said Karen.
"We've reached two cup finals, we're in another semi-final and we'd only lost once this year going into this game, but we didn't do ourselves justice on a big stage and in front of a very good crowd.
"We certainly had the chances but we didn't work the goalkeeper enough and credit to West Ham, they defended for their lives.
"The players are all upset because this was an ideal platform to show what we're all about and we didn't do that. Perhaps the occasion got to a few of them."
Spurs are back in FAWPL action with the long trip to Plymouth on Sunday (March 13) before their League Cup semi-final against Nottingham Forest on Sunday week (March 20).
Below: Lucia Leon in action at Upton Park
WEST HAM 1-0 SPURS LADIES
FA Women's Premier League South
Report from Khalid Karimullah at Upton Park
After moving to within 90 minutes of reaching their third cup final of the season on Sunday, Spurs Ladies made the short trip to the Boleyn Ground to take on local rivals West Ham on Tuesday night.
In front of a record crowd of 1,741, Karen Hills' side started the brightest. Alex Keown's perfectly-weighted free-kick looking for Wendy Martin had to be cleared away inside the area and Sophie McLean combined with Rosie Kmita, who broke away down the left flank before the latter curled in a delivery which forced West Ham goalkeeper, Beth Griffiths, to make a hurried catch with Martin again lying in wait.
The closest the hosts came to causing Spurs any trouble in the opening 15 minutes were hopeful passes up to Whitney Locke, who was kept quiet by Jenna Schillaci. Ronnell Humes broke into space before firing a powerful effort from just outside the box, which was cleared away.
Martin drifted into space before firing her effort past the upright prior to West Ham creating two quick chances. Karen Ray delivered a dangerous cross which came through to Katie Bottom, who on the turn saw her shot bobble through to Toni-Anne Wayne. Locke's pass almost arrived at the feet of the overlapping Gemma Abela, though Keown ensured the danger was cut out with a vital clearance.
Riana Soobadoo and Humes then released Martin, whose shot was saved by Griffiths.
Into the second half and with an hour on the clock, a key moment. Keown's floated delivery arrived at Lucia Leon who found the back of the net, but the linesman's flag was raised for offside.
Spurs piled on the pressure as Kelley Blanchflower, Soobadoo and Humes all went close only for West Ham to take the lead on 69 minutes. Laura Curtis went down inside the area, Bottom stepped up and sent Toni-Anne Wayne the wrong way.
As Spurs attempted to push for an equaliser, Humes' delivery from a corner came to Soobadoo, whose lob into the box was met by the head of Martin but somehow her header was cleared off the line.
Spurs Ladies: Toni-Anne Wayne, Mollie Kmita (Leanne Mabey 77), Alex Keown, Jenna Schillaci (c), Rosie Kmita, Sophie McLean, Shannon Moloney (Kelley Blanchflower 46), Riana Soobadoo, Wendy Martin, Ronnell Humes, Lucia Leon. Subtitutes (not used): Chloe Morgan, Amy Cooper, Eartha Pond, Leah Rawle.
Spurs Ladies Player of the Match - Lucia Leon.