A "floppy" pedal fits with a sticky master cylinder. The exact thing happened on my Sunbeam Rapier (called "Alpine GT" in the USA). For most of the stroke of the clutch pedal all you are doing is pushing against a spring, only the last quarter inch of movement does anything. If you keep pumping, the master cylinder piston will sometimes gradually move back and the clutch will work, but not for long.
I say take the master apart to find out what's wrong, if it looks at all damaged or worn buy a new one. A new one is a better bet than a repair (I've been there a few times!).
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.