Ben Wallace said the Russian army had suffered “a huge loss of life” and “only achieved international isolationism and humiliation”.
Ukraine claimed Russian casualties had reached 80,210 since the illegal invasion began.
The Kremlin announced the complete withdrawal from the city on Friday, ending more than eight months of occupation. As part of the retreat, Russian forces destroyed road and rail bridges over the Dnipro River.
Explosions at the Nova Kakhovka hydroelectric dam severed the rail and road link, damaged sluice gates and cut power lines and water pipes to the city. The dam was not breached.
Reports also emerged of Russian troops left behind changing into civilian clothes, or drowning as they tried to escape. Tonnes of equipment was left behind.
Russia still controls the left bank and about 70 percent of the Kherson region from which its artillery could still target the city. The Kremlin said the “temporary” capital for its puppet regime had been moved to Henichesk, a port city 130 miles from Kherson.
Mr Wallace said: “Russia’s announced withdrawal from Kherson marks another strategic failure for them.
“In February, Russia failed to take any of its major objectives except Kherson. Now with that also being surrendered, ordinary people of Russia must surely ask themselves: ‘What was it all for?’
“The Russian army has suffered a huge loss of life as a result of their illegal invasion and have only achieved international isolationism and humiliation.”
He pledged continued UK and international support as “while the withdrawal is welcome, no one is going to underestimate the continuing threat posed by the Russian Federation”.
As more Ukraine troops reached the centre of the city yesterday they were met by jubilant residents.
President Volodymyr Zelensky said: “We all feel uplifted together. We will see many such meetings in those cities and villages that are still under occupation. We don’t forget anyone, we won’t leave anyone.”