Sergey Brilev, a well known host on TV channel Rossiya, was described as a "propagandist for Putin".
Sanctions have also been imposed on RT's parent company, TV-Novosti, and managing director Alexey Nikolov.
Foreign Office sources said it would effectively mean RT could not return to UK screens after losing its licence.
Earlier in March, UK media regulator Ofcom revoked the channel's permission to broadcast, after deciding TV-Novosti was not "fit and proper" to hold a licence.
On Thursday, Culture Secretary Nadine Dorries said: "These sanctions will target those who are complicit in covering up the Russian state's actions.
"We will not hesitate to act further against individuals and organisations attempting to deceive people about this misguided war."
The 14 people and institutions on the latest sanctions list also include:
* state-owned media group Rossiya Segodnya, which operates the news agency Sputnik
* Sputnik editor-in-chief Anton Anisimov
* Aleksandr Zharov, chief executive of Gazprom-Media, which owns TV channel NTV
* Russia's National Defence Control Centre head Col-Gen Mikhail Mizintsev, who the government described as the "Butcher of Mariupol" for his role in the bombardment of the Ukrainian city.
Together, the US, EU and UK have already sanctioned more than 1,000 Russian individuals and businesses.
The UK's sanctions mean they cannot
* access assets or funds held in the UK
* do business with UK citizens or companies
* travel to or from the UK